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Convert a measure: pounds and kilos, °F and °C, feet and centimeters, cups and milliliters

A thermometer that reads in Celsius. A form that asks for your weight in kilograms and your height in centimeters. A recipe from back home in grams and milliliters. A baby weighed in pounds and ounces, and a grandmother who asks in kilos. This page changes one measure into the other. It shows the answer as you type, with the sum that made it and where the number in the sum comes from, so you can check it on paper.

Private by design. Nothing you type is sent anywhere, and nothing is kept: the page forgets the number when you close it. This page runs no analytics or tracking. How we handle privacy.

Good to know

The numbers, and where they come from

Every number here is from the conversion table of the National Institute of Standards and Technology (NIST), the U.S. government office for weights and measures: NIST Guide to the SI, Appendix B.8 (the page says it was updated August 18, 2025; we read it on October 10, 2026).

Temperature: °C = (°F − 32) ÷ 1.8, and the other way, °F = °C × 1.8 + 32.
1 inch = 2.54 centimeters. NIST marks this number as exact. A foot is 12 inches.
1 mile = 1.609344 kilometers. NIST marks this number as exact.
1 pound = 0.45359237 kilograms. NIST prints it rounded, as 0.4535924. A pound is 16 ounces, so 1 ounce is 28.349523125 grams; NIST prints 28.34952.
1 US cup = 236.5882 milliliters, 1 tablespoon = 14.78676, 1 teaspoon = 4.928922, and 1 US fluid ounce = 29.57353 milliliters.
1 US gallon = 3.785412 liters.
For cups, spoons, fluid ounces and gallons, NIST prints seven digits, so those answers are close ones, not exact ones. The page says "is about" for them.

Examples, worked by hand.

98.6 °F: (98.6 − 32) ÷ 1.8 = 37 °C. And 100.4 °F: (100.4 − 32) ÷ 1.8 = 38 °C.
37.5 °C: 37.5 × 1.8 + 32 = 99.5 °F.
An oven at 350 °F: (350 − 32) ÷ 1.8 is about 176.7 °C.
150 pounds: 150 × 0.45359237 is about 68.039 kilograms.
A baby of 7 pounds 8 ounces: 7 × 16 + 8 = 120 ounces. 120 ÷ 16 × 0.45359237 is about 3.402 kilograms.
68 kilograms: 68 ÷ 0.45359237 is about 149.91 pounds. That is about 149 pounds and 14.6 ounces.
5 feet 7 inches: 5 × 12 + 7 = 67 inches. 67 × 2.54 = 170.18 centimeters.
170 centimeters: 170 ÷ 2.54 is about 66.93 inches. That is about 5 feet and 6.9 inches.
10 miles: 10 × 1.609344 is about 16.09 kilometers. 5 kilometers: 5 ÷ 1.609344 is about 3.11 miles.
250 milliliters: 250 ÷ 236.5882 is about 1.06 US cups. 1 teaspoon is about 4.93 milliliters.

A program checks these examples, and 400 made-up counts done a second way, every time the page is built.

Where these counts trip people up

Temperature is not one multiplication. The 32 comes off first: 98.6 °F is 37 °C, not 54.8.
Ounces are sixteenths, not tenths. 7 pounds 8 ounces is 7.5 pounds, not 7.8.
Inches are twelfths. 5 feet 7 inches is 67 inches, not 5.7 feet.
An ounce of weight and a fluid ounce are two different measures. One weighs a thing; the other says how much room a liquid takes.
A cup of flour and a cup of water do not weigh the same. This page does not change cups into grams, because that depends on what is in the cup.
Rounding early moves the answer. The page keeps the whole number until the end and rounds once.

What this page does not do

It is not for working out a dose of medicine. It does not know any medicine. A pharmacist can say how to measure one.
It does not say what a temperature means. It changes the number, and that is all. Our fever guide has what the health agencies say.
It uses the U.S. cup, fluid ounce and gallon. NIST lists the Canadian and U.K. gallon and fluid ounce as different measures, and this page does not use them.
A tablespoon and a teaspoon here are the measures, not the spoons in a drawer.
It shows temperature to a tenth of a degree, kilograms to three places and the rest to two.
It takes numbers up to 999,999.999, with up to three places after the point.
It keeps nothing. To keep an answer, write it down.

Tools that go with this

Make a recipe bigger or smaller: every amount multiplied by the same number.
Unit price: which pack costs less for the same amount.
Gas for a trip: what the gas costs, and how far the money goes.
Weight log: a weight written down each day.
Baby log: feeds, diapers and sleep, written down.
Percent: a part of a number, worked out.
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A count, not advice. This tool changes a number from one measure to another. It does not know your health, your medicine or your recipe, and it is not medical advice. If anyone is in danger, call 911. If things are so heavy that you are thinking about ending your life, call or text 988 (in the U.S.), or open Get help now.

The tool and the wording around it were written with AI (Claude) for Scarlet Beast (our AI policy); the conversion numbers are NIST's. There is no AI inside this tool: it only adds, multiplies and divides. It has been checked by a program, not yet by people using it for a real form or recipe. It keeps nothing, so it has no line on My data on this device. Also in Spanish: Convertir medidas. Found a mistake? Email [email protected].