About Your Equation
Your Equation is a free library of 548 engineering and science formulas, from GCSE and A-level through to MSc and defence engineering. It was built for students and engineers who want to understand a formula, not just look it up.
What you get on every formula page
- The equation, with every symbol defined and its units.
- A live calculator that solves for any variable, not just the answer at the bottom.
- A worked example with the arithmetic shown step by step.
- A ranked view of which inputs matter most to the result, and how it responds as each one changes.
- Assumptions, common mistakes, typical uses and the maths you need to follow it.
- Related formulas, and a practice mode with generated questions and full solutions.
Who it is for
The library was first put together for MSc military engineering students, so it includes vehicle dynamics, stress analysis, pressure vessels, sensors, navigation and ballistics alongside the core mechanics, thermodynamics, electrical and chemistry topics. The foundations sections cover GCSE and A-level maths, physics and chemistry, so you can work back to the basics when something does not make sense.
How to use it responsibly
The formulas are from the open literature and are intended for study and first-order estimates. Check results against an authoritative source before relying on them, and never use them alone for safety-critical design. Most formulas have limits on where they apply: the assumptions on each page say what they are. Read the terms and disclaimer for the full position.
Free, with no tracking
There are no accounts, no sign-up and no advertising. All the calculations run in your browser, and what you type stays on your device. See the privacy policy for details.
Spotted a mistake?
Please tell us. Corrections and suggestions are the quickest way to make the library better: see the contact page.