Tools · Emergency · Index A–Z · Calculator
Works with no internet. Type an amount, or pick a kind of measurement. The calculators below do the everyday math for building, water, power, food and travel. For how the formulas work, see the Practical Math guide.
Tap one to open it. Every result is also shown in metric. These do arithmetic only — check anything that matters (a load, a dose, a wire size) against the guides and books.
Conversion factors are the exact legal definitions (1 inch = 2.54 cm; 1 pound = 0.45359237 kg; 1 US gallon = 231 cubic inches). Food weights per cup are averages from USDA food tables and vary with how you fill the cup.