Deflection limits: span/250

Keep beam deflection under span/250 generally, span/360 where people will notice a bouncy floor.

Why it works

Serviceability limits from building codes. A 4 m joist should sag no more than ~11 mm under load — stiffness governs long before strength does.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

Open Beam Bench — deflection & stress →

More in Mechanical

• The bolt-torque shortcutTightening torque ≈ 0.2 × preload × bolt diameter (dry steel).
• Torque mostly fights frictionRoughly 90% of tightening torque is lost to friction; only ~10% actually stretches the bolt.
• Depth beats width, cubedDouble a beam’s depth and its deflection drops 8-fold. Double its width and it only halves.
• Keep water at 1–2.5 m/sSize pipes so water flows between about 1 and 2.5 m/s.

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