Every formula you keep looking up, on one page: maths, physics, chemistry and biology by level, plus SI units, prefixes, conversions and constants. Search it, filter it, convert with it, print one subject on one sheet.
Level
Unit converter
Factors are exact where the unit is defined exactly (inch, pound, atmosphere, calorie, kWh); the rest are rounded from NIST SP 811.
Where these were checked, and a warning
Constants follow CODATA 2022 (the 2019 SI redefinition made h, e, kB and NA exact); conversions follow NIST SP 811 and the SI Brochure; formulas follow the published data booklets and equation sheets of Cambridge International, AQA, Edexcel, OCR, the IB and the College Board (AP). Boards differ in symbols and in rounded values (g = 9.8, 9.81 or 10; molar volume 24 or 22.4 dm3): in an exam, the sheet your board gives you wins. Found a mistake? Tell us. The full list of sources is in sources.md next to this page.
