Weight & Mass Converter
Convert weight and mass between grams, kilograms, pounds, ounces and more.
Results update as you type.
About this calculator
A weight converter changes a mass between metric units (milligram, gram, kilogram, metric ton) and imperial/US units (ounce, pound, stone, US ton, imperial ton), plus the carat used for gemstones. Every value is converted through kilograms as the base unit so any pair works in both directions.
The conversions rest on fixed definitions: 1 pound = 0.45359237 kg exactly, 1 ounce = 1/16 pound ≈ 28.35 g, 1 stone = 14 pounds and 1 metric ton = 1,000 kg. Strictly speaking these are units of mass rather than weight, but in everyday use on Earth the two are treated as the same thing.
Worked example: to convert 5 kilograms to pounds, multiply by 2.20462, giving about 11.02 pounds. Going back, 150 pounds is 150 × 0.45359237 ≈ 68.04 kg. A results table restates your mass across every unit from the milligram to the imperial ton at once, so a recipe in ounces or a parcel in kilograms is a single glance away.
Frequently asked questions
How many pounds are in a kilogram?
One kilogram equals about 2.20462 pounds, and one pound is 0.45359237 kilograms. That pound-to-kilogram figure is an exact international definition.
How many ounces are in a pound?
There are exactly 16 ounces in a pound. One ounce is about 28.35 grams, so a pound is roughly 453.6 grams.
What is a stone in kilograms?
One stone equals 14 pounds, or about 6.35 kilograms. The stone is still commonly used for body weight in the UK and Ireland.
How many grams are in an ounce?
In this weight converter one ounce is about 28.35 grams. This is the avoirdupois ounce used for everyday weight; the troy ounce used for precious metals is heavier, about 31.10 grams.
What is the difference between a US ton and a metric ton?
A US ton (short ton) is 2,000 pounds, about 907 kg. A metric ton (tonne) is 1,000 kg, about 2,205 pounds, and the imperial or long ton is 2,240 pounds, about 1,016 kg.
Is weight the same as mass?
Not strictly — mass is the amount of matter and weight is the force gravity exerts on it. On Earth’s surface they are proportional, so converters like this one treat kilograms and pounds as interchangeable measures.
What is a carat?
A metric carat is exactly 200 milligrams (0.2 g) and is used to weigh gemstones and pearls. It is different from the karat that measures gold purity.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/weight-mass/curl
curl "https://calculator.free/api/v1/weight-mass/?amount=1&from=kg&to=lb"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/weight-mass/?" + new URLSearchParams({
"amount": "1",
"from": "kg",
"to": "lb"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.