Start here · Essential guide
Units and Dimensional Analysis for Engineers
How to use units and dimensions to check equations, spot wrong formulas and catch mistakes early, with simple worked examples and the limits of the method.
Engineering Fundamentals
Units and Estimation
Working safely with units, magnitudes and quick estimates.
Back-of-the-Envelope Estimation
Learn how to make fast, rough estimates with round numbers to sanity-check results, with simple illustrative examples and notes on when an estimate is enough.
Converting Between Unit Systems Without Errors
A reliable way to convert units by multiplying by fractions equal to one, with worked examples for speed, length, area, pressure and temperature, and common pitfalls.
Sanity Checking Your Calculations
Practical habits for catching calculation mistakes: limit cases, unit checks, rough estimates, trend checks and independent methods, with small worked examples.
Scientific Notation and Working with Very Large or Small Numbers
How to write numbers as powers of ten and calculate with them by hand, including multiplication, division, addition and roots, with checked examples and common slips.
SI Units and Prefixes Refresher
A quick refresher on the seven SI base units, common derived units and the prefixes from nano to giga, with conversion practice and mistakes to avoid.
Significant Figures and Rounding in Practice
How many digits to report, how to round without piling up errors, and why false precision misleads readers, with small worked examples you can check by hand.
Tolerances and Measurement Uncertainty Basics
What a tolerance or uncertainty figure means, how they differ, and how errors combine in simple stack-ups using worst-case and root-sum-square methods.
Related topics
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Requirements and Specifications Capturing what a system must do and proving that it does. Systems Thinking Seeing how parts, interfaces and feedback shape whole systems. Math Refreshers Short refreshers on the maths engineers use, with checked examples. Components and Datasheets Reading datasheets and understanding common parts.