Recipes in cups, hardware in inches, manuals in millimeters, weather in Celsius when you think in Fahrenheit: units collide daily. This converter handles the four categories that cause the most friction.
Updated August 15, 2026, after a fresh review, with updated visuals and links.
Pick a category, type the value, convert. The quick-reference tables below cover the conversions worth memorizing.
The conversions worth knowing cold
Length anchors: an inch is exactly 2.54 cm, a foot is 30.48 cm, a mile is 1.609 km, a meter is 39.37 inches. With those four, most daily conversions become mental math.
Weight anchors: a kilogram is 2.205 pounds, a pound is 453.6 grams, an ounce is 28.35 grams. For cooking, 100 grams of flour is about three quarters of a US cup (flour settles; scales win).
Temperature needs formulas, not factors: F to C subtract 32 then multiply by 5/9; the famous pair to remember is 32 F = 0 C and 82 F = 27.8 C. Room temperature on both scales tells you if your answer smells right.
Worth remembering
- Kitchen rule: volume measures of dry goods vary with packing; a cheap scale plus grams converts any recipe reliably.
- Tire placards list pressure in both PSI and kPa: 32 PSI is about 220 kPa, multiply PSI by 6.895 to check.
Frequently asked
How many centimeters in an inch?
Exactly 2.54 cm by international definition since 1959. Twelve inches make a foot, so a foot is 30.48 cm.
What is 350 F in Celsius?
Subtract 32, multiply by 5/9: 318 times 5/9 equals about 176.7 C, which is why many recipes say 180 C.
