By accessing or using this site, you agree to these Terms of Use. If you do not agree, please don't use the site.
Rules of Thumb is a collection of free, browser-based reference calculators organised into discipline-specific areas — currently Environmental, Engineering, Finance, Control Systems, and Computers, with more areas planned over time. Every calculator requires no installation, account, or sign-up, and all calculations run locally in your browser — see our Privacy Policy for details. New areas and tools may be added to the site from time to time; this policy and these terms apply to all of them unless a specific tool says otherwise.
Read this carefully. The calculations, charts, and reference data on this site are provided for general informational, educational, and preliminary-estimation purposes only. They are not a substitute for certified engineering calculations, calibrated instrumentation, equipment manufacturer data, or the advice of a qualified, licensed engineer.
Tools in the Finance area do not constitute financial, investment, tax, or legal advice, and are not a substitute for a bank, lender, licensed financial advisor, or accountant. Figures such as interest rates, historical returns, property taxes, and insurance costs are illustrative estimates, not quotes, offers, or forecasts — your actual terms from any real institution will differ.
Tools in the Control Systems area, and any other simulations on this site, model idealised systems and omit many real-world effects (nonlinearity, time delay, noise, saturation, and more). They are intended to build intuition and must not be used to design, tune, or validate a real control system, mechanism, or safety function without proper analysis of the actual system.
These tools must not be relied upon for safety-critical decisions, life-safety systems, custody-transfer measurement, regulatory compliance, or binding financial commitments. Climate, altitude and location reference data are indicative averages, not measured or forecast values for any specific date.
The site, and all information on it, is provided “as is” and “as available”, without warranties of any kind, whether express or implied, including but not limited to warranties of accuracy, merchantability, fitness for a particular purpose, or non-infringement. You are solely responsible for independently verifying any result before relying on it.
To the maximum extent permitted by law, we exclude all liability for any direct, indirect, incidental, special, or consequential loss or damage — including loss of profit, data, or business — arising from your use of, or inability to use, this site, even if we have been advised of the possibility of such loss.
Nothing in these terms excludes or limits liability that cannot lawfully be excluded or limited, including liability for death or personal injury caused by negligence, or for fraud, under the laws of England and Wales (including the Consumer Rights Act 2015 where it applies) or any other law that applies to you and cannot be contractually excluded.
The design, branding, original written content, and underlying code of this site are © [year] [your name or business name], unless otherwise stated. The physical formulae and engineering principles used are general scientific knowledge and are not owned by anyone. You're welcome to use the tools for personal or professional reference; please don't copy, scrape at scale, redistribute, or re-host the site's code or design without permission.
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This site is hosted using Cloudflare Pages and loads typefaces from Google Fonts. Your use of the site is also subject to the relevant terms of those providers where applicable. See our Privacy Policy for more on what data each of these involves.
The site is provided on a best-effort, “as available” basis. We don't guarantee uninterrupted access, accuracy, or error-free operation, and we may modify, suspend, or discontinue the site, or any part of it, at any time without notice.
These terms are governed by the laws of England and Wales, and the courts of England and Wales have non-exclusive jurisdiction over any dispute arising from them. If you are a consumer resident elsewhere — including in the EU/EEA or another country — any mandatory consumer-protection laws of your country of residence will still apply to you and are not overridden by this clause.
If any provision of these terms is found unenforceable, the remaining provisions continue in full effect.
We may update these terms from time to time. We'll update the “last updated” date above when we do.
Questions about these terms can be sent to [contact email].