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Every calculator and simulator on the site, one flat alphabetical list — or browse by popular votes.

139 tools (JavaScript enables live filter) 3-2-1 Backup CalculatorThree copies, two media, one off-site — but which of the three actually protects you? Put your own failure rates in and see what each step is worth.Computers A/B Test Sample Size CalculatorSample size per variant for a target lift, the minimum effect a given sample can detect, and why stopping early when it looks significant invents results.Mathematics Acids & BasesFind the pH of strong and weak acids and bases, titrate one against another, watch a buffer hold its pH, and see which form of an acid is in the beaker.Materials and Elements Air & Gas DensityHow dense air and ten other gases are at any temperature and pressure, with humid air, the real-gas correction and where a gas would condense.Materials and Elements Altitude & DepthPressure, temperature, oxygen and force from the stratosphere to the ocean floor — explore any altitude or depth, from Everest to Challenger Deep.Environmental Ball and Beam Control SimulatorThe classic ball-and-beam control system — tune PID gains to balance a rolling ball, and see exactly why proportional-only control fails.Control Systems Battery Sizing & RuntimeHow long a battery bank really lasts: depth of discharge, the Peukert effect that costs lead-acid half its capacity at high draw, and inverter losses.Electrical Beam Deflection & Stress CalculatorSimply-supported and cantilever beam deflection and stress calculator, with live shear and bending-moment diagrams for common load cases.Mechanical Bearing CalculatorDeep-groove ball bearing L10 life to ISO 281 — combined radial and axial load, plus the dynamic rating C you need to hit a target life in hours.Mechanical Beverage Cooling SimulatorA real 2D transient heat-transfer simulation — watch a can or bottle cool in a fridge, freezer or ice bath, with live convection and radiation physics.Physics Bit CalculatorA visual programmer's calculator — convert between binary, hex, octal and decimal, flip bits by hand, and watch bitwise operations combine column by column.Computers Black Body & Colour TemperatureHeat anything and it glows. Set a temperature and see its colour, its spectrum, Wien’s law, the Stefan–Boltzmann power and how much is light.Physics Blood Alcohol CurveHow a night of drinking might move blood alcohol over time, with the uncertainty shown. It cannot tell you whether you are fit to drive.Health BMI CalculatorBody mass index plotted on a full height/weight chart, colour-coded by WHO category — see exactly where you sit, not just a single number.Health Bode PlotBuild a transfer function from gain, poles, zeros and integrators and watch the Bode magnitude and phase plots live, with gain and phase margin computed.Control Systems Bolt Torque & Preload CalculatorBolt torque and preload calculator — pick a bolt size, grade, and lubrication condition to get the target tightening torque and resulting clamp load.Mechanical Car Finance CalculatorCar loan and hire-purchase calculator for the UK and US — monthly payments, total interest, deposit vs balloon (PCP), trade-in, fees and a schedule.Finance Circlip CalculatorDIN 471/472 circlip calculator — groove diameter, width, depth and a thrust rating computed from your own shaft material, not a fixed table.Mechanical Clock Angle CalculatorThe angle between the hour and minute hands at any time, with the formula and the working shown — plus every time the hands overlap or form a right angle.Mathematics Coffee Grinder SimulatorWatch beans bounce in a blade grinder or work down through a burr set. Change the gap, the dose and the speed; see the grind spread, the effort and the heat.DIY Collision SimulatorMulti-ball collisions and Newton's Cradle, from perfectly elastic to perfectly inelastic — up to 10 balls, with real momentum and energy conservation.Physics Column Buckling CalculatorEuler column buckling calculator with automatic Johnson-formula fallback for short columns — critical load and stress for any end condition.Mechanical Compound Interest CalculatorCompound interest calculator — model savings or investment growth with adjustable contribution, rate and compounding frequency, as a live curve.Finance Concrete Mix CalculatorCement, sand, aggregate and water for any concrete volume and grade — real mix ratios and the dry-volume correction, not a guess.Materials and Elements Countdown & Working DaysHow long until any date, in every unit at once — and how many working days that actually is, with the bank holidays worked out rather than guessed.Mathematics Currency ConverterFree currency converter using European Central Bank reference rates via Frankfurter — convert between USD, EUR, GBP, JPY and 20+ currencies.Finance Data Transfer Time CalculatorHow long to download or upload a file at a given speed — movies, games, backups. Same estimates as the Internet Speed Test use-cards.Computers Debt Payoff CalculatorCompare the snowball and avalanche debt payoff strategies side by side — payoff time, total interest, and a live balance-over-time chart for each.Finance Depth of FieldNear and far limits, hyperfocal distance, and the aperture where diffraction costs more than stopping down buys — plus why the lens barely matters.Physics Dice Roller & Coin TossRoll d4 to d100 and flip coins in 3D, with the exact distribution behind every roll — advantage, exploding dice, and dice that beat each other in a circle.Mathematics Dive Depth & Ascent GuidePublished ascent-rate guidance for scuba, technical and breath-hold diving, depth bands from open water to the Challenger Deep, and how submersibles differ.Environmental Earthquake Magnitude & Richter ScaleWhat each earthquake magnitude releases and does, famous quakes at every level, the equations, and a map of 53 years of M6+ quakes on the plate boundaries.Environmental Egg Timer CalculatorThe real physics of boiling, poaching, frying and scrambling eggs — any egg type, size, doneness and heat, with an actual countdown timer and audio alert.DIY Electrical CircuitOhm's law solver plus Kirchhoff's laws — a two-loop circuit solved step by step, a junction current calculator, and series/parallel resistor networks.Electrical Electromagnetic Spectrum ExplorerWavelength, frequency and photon energy together across the whole spectrum — visible light in true colour, and the Planck curve for any temperature.Physics Energy Cost CalculatorWhat your appliances actually cost to run. Add common or custom appliances, pick a country, and see the cost per day, week, month or year.Environmental Engine Cycle SimulatorFive engines animated — petrol, diesel, 2-stroke, Atkinson and Wankel rotary — with exact slider-crank motion, valve timing and the indicator diagram.Mechanical EV Charging & Running CostWhat an electric car actually costs to run: charge time with the real power taper, cost per mile at home, off-peak and rapid tariffs, against petrol.Environmental Feels Like TemperatureWind chill, heat index and apparent temperature — including the 17°C band where neither NWS formula applies and most calculators just give up.Environmental FIRE CalculatorFinancial independence / early retirement calculator — your FIRE number from spending and safe withdrawal rate, years to reach it, and your Coast FIRE number.Finance First-Order Lag & Dead TimeFind a process time constant and dead time from a step test, see the 63% rule on the curve, and get Ziegler-Nichols and lambda tuning from it.Control Systems Fluid PropertiesViscosity and density vs temperature for 21 fluids, on ASTM D341 for oils and Vogel for water. Compare them, get Reynolds number, add your own datasheet.Materials and Elements Galileo Drop ExperimentFree-fall calculator and drop race — t = √(2h/g) alongside a real drag simulation. Drop from 0.3 m to 300 m, on Earth, the Moon or Mars, with custom objects.Physics Gear Train CalculatorGear train calculator — overall ratio, output speed, output torque and rotation direction for up to three meshed stages, with mesh efficiency losses.Mechanical Geometry — 2D & 3DThirty-six shapes — seventeen flat, nineteen solid. Rotate every solid in 3D, fold it flat along real hinges, and see where each formula comes from.Mathematics Graphing CalculatorPlot up to eight functions at once, pan by dragging and zoom with the wheel or a pinch — a fast, offline, Desmos-style graphing calculator.Mathematics Guitar ChordsChord shapes worked out from the tuning itself, so capos and alternate tunings just work. Strum them, and slow the strum right down.Music and Acoustics Guitar TunerA browser guitar tuner that reads pitch to a fraction of a cent, plus the exact frequency of every string in standard, drop D, DADGAD and open G at any reference A.Music and Acoustics Gym CompanionPick a routine or build your own from 69 exercises, add your own lifts, and run the session with a set tracker, a rest timer that beeps, and live volume.Health Heart Rate Zones & Max HRTraining zones from four max heart rate formulas at once, so you can see how far apart they are — plus why %HRmax and Karvonen %HRR zones differ.Health Heat Loss & Heat Pump SizingWork out a home's heat loss in kW from fabric U-values and ventilation, size the heat pump, and see how much bigger the radiators have to be.Environmental Hydraulic Force CalculatorPressure, area and force in a hydraulic system — F = P·A and Pascal's force multiplier — with a live to-scale cylinder visual.Mechanical Ideal GasSqueeze and heat a gas and watch the molecules, solve PV = nRT in any units, see how fast the molecules go, and see where a real gas stops being ideal.Materials and Elements Inclined PlaneA block on a ramp, simulated with real friction and real motion — set the angle, mass and friction, and watch whether it holds, slides or needs a push.Physics Inflation CalculatorWhat a price in any past year is worth in today's money, and what today's money will be worth later. UK and US consumer price indices, since 1900.Finance Integral Windup & Anti-WindupWhat happens when a PI controller keeps integrating against an actuator that is already flat out, and what clamping and back-calculation actually fix.Control Systems Internet Speed TestA real, live download and latency test with graphs and a moving average — then what your speed actually means in 4K streams and game installs.Computers Latency LadderA cache hit, a memory read, an SSD, a disk seek and a packet across an ocean — stretched so one nanosecond is one second, where the gaps become legible.Computers Lenses & MirrorsMove an object in front of a lens or mirror and see the rays, where the image forms, whether it is real or virtual, upright or upside down, and how big it is.Physics Lightning DistanceCount the seconds from flash to thunder and get an honest band, not a false figure — plus the thing the count is really for: whether you are already in range.Environmental Limits & Fits CalculatorISO 286 limits and fits calculator — hole and shaft tolerances, deviations, clearance or interference, and how thermal expansion shifts the fit.Mechanical MagnetismSee the field of a magnet, wire or coil, what it does to a moving charge or a current, how a changing field makes a voltage, and the Earth’s field at your city.Physics Mass-Spring-DamperSimulate a second-order mass-spring-damper system: damping ratio, natural frequency, and the free response across all four damping regimes.Physics MetronomeA metronome scheduled against the audio clock, with editable accents, subdivisions, swing, odd meters, and a trainer that speeds you up or drops out bars.Music and Acoustics MoleculesTwenty-six molecules in 3D, with the bond angles relaxed from repulsion rather than looked up — and the places that rule of thumb is wrong.Materials and Elements Moles & SolutionsType a formula for its molar mass and composition, convert grams to moles, molecules and gas volume, and work out how to make, dilute and measure solutions.Materials and Elements Moon PhaseThe Moon’s phase, moonrise and moonset for any city and date, its path in the sky, distance and size, the next eclipses and the year’s named full moons.Environmental Mortgage CalculatorMortgage calculator that models your market, not just your currency — reverting fixed rates, semi-annual compounding, stamp duty, CMHC and LMI.Finance Motor Starting & InrushFull-load current, locked-rotor inrush, and what star-delta, soft starters and VFDs actually cost you in torque. Breaker trip windows and supply voltage dip.Electrical Nozzle SimulatorA converging-diverging nozzle you can drive. Sweep the back pressure and watch it choke, grow a shock, separate, and blow Mach diamonds out of the bell.Mechanical O-Ring CalculatorO-ring groove and gland design calculator — pick a standard AS568 cross-section, choose static or dynamic sealing, and get depth, width and squeeze.Mechanical On-Off Control & HysteresisHow a thermostat deadband sets the cycling rate, why oversizing causes short-cycling that wrecks compressors, and why cycling peaks at half load.Control Systems Orbital MechanicsCircular and elliptical orbit calculator — period, velocity and escape velocity from Kepler's laws, with a live animated orbit and ISS-like presets.Physics Paint Colour MixingMix paint colours the way real pigments combine — a subtractive RYB colour-wheel model, not naive RGB averaging, so blue and yellow make green.DIY Paint Coverage CalculatorHow much paint you actually need — room dimensions to litres and cost, with real coverage rates by paint type, surface porosity, and number of coats.DIY Password Strength & Crack TimeEntropy in bits and time to crack against five classes of attacker, showing why a five-word passphrase beats eight random characters by thousands of times.Computers Pendulum SimulatorSingle, double and triple pendulum simulator — real Lagrangian mechanics, RK4-integrated and animated. Watch a clean swing become full chaotic motion.Physics Pension Pot CalculatorProject your pension pot in the UK, US, Canada or Australia: employer money, tax relief, charges and inflation, then the income it pays after tax.Finance Percentage CalculatorPercent of, percent change, reverse VAT, markup vs margin, stacked discounts and percentage points — twelve calculations, each with the arithmetic shown.Mathematics Periodic TableAll 118 elements with a 3D nucleus and electron-shell viewer, five real uses and five common compounds each, and every property ranked against the rest.Materials and Elements Piano ChordsAny chord on a properly drawn keyboard, with every inversion, a fingering for each hand, and a progression voiced so your hand barely moves.Music and Acoustics PID ControlTune a PID controller and watch the closed-loop step response change as you move it — overshoot, rise time, settling time and steady-state error, live.Control Systems Pipe Flow & Pressure Drop CalculatorPipe flow and pressure drop calculator using the Darcy–Weisbach equation and Moody diagram, with a live velocity profile and wall shear gradient.Mechanical Power Factor CalculatorPower factor correction calculator — kVAR and the actual capacitor in µF, for three-phase delta or star and single phase, with currents before and after.Electrical Precision Timer & StopwatchStopwatch, timers, alarms, a world clock, an interval trainer and a reaction test — drift-corrected, with the lap statistics a phone does not give you.DIY Projectile Motion & Golf Ball FlightTwo ballistics simulators in one — classic no-drag projectile motion, and a real 3D golf ball flight simulator with drag, Magnus lift and wind.Physics PsychrometerPsychrometric calculator — dew point, wet-bulb and enthalpy, with relative, absolute and specific humidity and mixing ratio kept apart, on live charts.Environmental PV DiagramPressure-volume diagram for the ideal thermodynamic cycles — Otto, Atkinson, Diesel, Brayton and Carnot — with state-by-state work, heat and efficiency.Mechanical Radioactive Decay & Half-LifeWatch a sample decay atom by atom, see the half-life curve appear, run it backwards to find an age, and see how active a quantity of material is.Physics RAID CalculatorWork out usable capacity, fault tolerance, efficiency, throughput and rebuild risk for any RAID level — and compare them all at a glance.Computers Reacting Masses & YieldType a chemical equation to balance it, then find the limiting reagent, the theoretical and percentage yield and the atom economy, or the masses you need.Materials and Elements Reading MusicEvery note on the stave in any clef, drawn properly, with the mnemonics, the landmarks that replace them, and a trainer that works out which notes you are slow on.Music and Acoustics Refraction & Diffraction CalculatorSnell's law, Fresnel reflection, a prism that splits white light, and single-slit, double-slit, grating and Airy diffraction, every ray and pattern drawn live.Physics RelativityRelativity from one fact: everyone measures light at the same speed. Watch a light clock slow, see why 'now' is not universal, find the 38 microseconds GPS needs.Physics Rent vs Buy CalculatorThe real comparison: net cost of buying against renting and investing the difference — not just monthly payment vs rent.Finance Resistor Colour Code Calculator4-band resistor colour code calculator — pick band colours to get ohms, or enter a resistance to see the nearest standard colour bands. IEC 60062.Electrical Rocket Equation & Delta-v BudgetMulti-stage rocket equation calculator — real vehicle presets (Falcon 9, Saturn V), an animated launch burn, and a delta-v budget vs. mission targets.Physics Room Colour VisualiserPaint a 3D room with your own mixed colours and see how they really look — bounced light, sheen from matt to gloss, six rooms in three sizes, and export to JPG.DIY Running, Cycling & Swimming PaceDistance, time, pace and speed for running, cycling and swimming — with real population percentiles and pro, average and beginner reference times.Health Salary ConverterConvert pay between hourly, daily, weekly, monthly and annual, estimate take-home after tax, and compare net pay across locations.Finance Sampling & AliasingSee the Nyquist limit in action: sample a sine wave too slowly and watch a false, lower-frequency 'alias' appear. With the fold formula and a live plot.Control Systems Scales, Modes & FretboardAny scale or mode drawn on the neck, with real note spelling, computed position boxes, the chords that fit it, and a drone to play against.Music and Acoustics Scientific CalculatorA full scientific calculator that shows how it read your expression, which angle mode it is in, and the exact floating-point value.Mathematics Screen Refresh Rate TestMeasure the refresh rate your browser is really presenting at, from 60 Hz to 500 and beyond — with frame-time jitter, dropped frames and 1% lows.Computers Screen Size & Viewing DistanceHow far to sit from a screen, and whether you would see the difference between 1080p, 4K and 8K at that distance — pixels per degree against your acuity.Computers Screw, Stud & Tap Drill SizingWhat fixing to actually use for a given load and wall type, UK stud spacing standards, and a wood screw sizing reference — with a live wall cross-section.DIY Solar PV EstimatorEstimate annual and monthly output of a solar PV array: location, system size, panel tilt and orientation — all in your browser.Environmental Solar SystemEvery planet in 3D from its real orbital elements — at true scale and compressed, size against size, and a head-to-head on ten measures.Physics Sound Levels & DecibelsEveryday sounds at any distance, added together properly. Why 60 dB plus 60 dB is 63, why twice the distance costs 6 dB, and how long 100 dB is safe for.Music and Acoustics Specific Heat & Heat TransferThe energy to heat, melt or boil something, what happens when hot and cold mix, and how heat leaks through a wall and away by convection and radiation.Physics Speed of Sound & Mach ConeFly anything from a bullet to Concorde: the speed of sound at any altitude, the Mach cone, when the boom reaches the ground, and why some never do.Physics Spring Rate CalculatorHelical compression spring calculator — spring rate, deflection, coil shear stress with the Wahl correction factor, and the maximum safe load before yielding.Mechanical Standing Waves & SuperpositionWatch two waves add, cancel, beat and freeze into a standing wave; then find the notes a string or a pipe can make and shake it at any frequency to see resonance.Physics Star Map & ConstellationsA live star map for any place and any moment: the whole sky, or the view towards one horizon. Every star named, every constellation with its story and its numbers.Physics Statistics & ProbabilityStandard deviation, z-scores, quartiles and outliers, with box, histogram and Q–Q plots — plus a real Galton board that builds the bell curve live.Mathematics Steak Timer & Doneness CalculatorSteak cooking times from real heat conduction — by thickness, not weight — with a live timer that says when to flip, pull and rest.DIY Stopping Distance CalculatorTwo cars braking side by side, to scale. Highway Code figures against real friction for wet, snow and ice — and how fast you arrive where the slower car stopped.Mechanical Student Loan CalculatorUK student loan repayment projected over your career — Plans 1, 2, 4, 5 and postgraduate, with salary growth, interest and the write-off date.Finance Subnet CalculatorWork out network and broadcast addresses, subnet mask, host range and usable hosts for any IPv4 CIDR block — and split a network into subnets.Computers Sun PhaseSunrise, sunset, solar noon and twilight for any place and day: the sun’s height through the day, its path across the sky and the year at a glance.Environmental SUVAT CalculatorEnter any three of s, u, v, a and t and get the other two, with the equation used and the working shown — including the cases that have two answers or none.Physics Sweat Rate & HydrationWork out your own sweat rate from body mass before and after exercise, how much to drink to stay inside the 2% threshold, and why generic advice fails.Health TDEE & Calorie CalculatorTotal daily energy expenditure from the Mifflin-St Jeor equation, the most validated BMR formula — plus honest guidance on picking your real activity level.Health Tea & Coffee Brewing CalculatorPick the exact shade of tea you want and get the brew time, or dial in the coffee-to-water ratio for any brew method — real extraction kinetics.DIY Tide Curve & Rule of TwelfthsThe height of tide at any hour by the rule of twelfths, the window you can cross in, and an honest look at the assumption that really ruins it.Environmental Time Zone ConverterConvert times across 215 cities and every IANA time zone, grouped by region, with a world map showing who is awake and where the sun actually is right now.Environmental Tip Calculator & Bill SplitterTip calculator with a real regional-norms guide, even and uneven bill splitting, and correct tip-on-pre-tax handling — not just a percentage of the total.Finance Traffic Jam SimulatorWatch a traffic jam appear from nothing on a circular road. Set reaction time, headway, acceleration and driver spread, and see the stop-and-go wave crawl backwards.Control Systems Transformer CalculatorTurns ratio, voltage, current and power for any transformer — drag the primary and secondary turns and watch the coils and the physics change together.Electrical Trigonometry & PythagorasRight triangle solver from any two known values, plus an animated unit circle tracing sine and cosine waves — Pythagoras and SOH-CAH-TOA in one tool.Mathematics Typing Speed TestA typing test that shows its working: live WPM with adjustable smoothing, per-keystroke timing, your slowest keys, and where the result ranks.Computers Unit ConverterConvert length, mass, pressure, energy, power, temperature, force, density, data, currency and more — type a whole conversion like “12 ft to m”.Mechanical Uptime & SLA CalculatorTurn any availability figure into real downtime per year, month, week and day — and see what a chain of dependencies does to it, because availability multiplies.Computers Waist-to-Height Ratio CalculatorOne measurement BMI cannot make: waist against height, the cases where the two disagree in both directions, and why a tape measure beats a set of scales.Health Week Number CalculatorISO 8601 week numbers for any date, the dates any week covers, which years have 53 weeks, and where the US Sunday-start convention disagrees.Mathematics Where You StandPlace your height, weight, income, net worth, age and footprint on the world and on your country, with the map of where the average person is like you.Health Wind TunnelA live wind tunnel: watch air flow round a wing as you change the angle, slat, flap and spoiler, then go supersonic and see the shock waves.Physics Wire Gauge & Voltage Drop CalculatorPick the right AWG wire for the current and distance, and see the actual voltage drop — real NEC ampacity and resistance tables, not a rule of thumb guess.Electrical World AtlasEvery country on one map, equal-area or Mercator. Population, GDP, land area and highest points — sortable, and grouped by continent, NATO, EU and G7.Environmental

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