Weight & Mass Converter (mg, g, kg, lb, oz, stone, ...)
Convert a weight or mass between metric units (milligrams through metric tons) and imperial/US units (ounces, pounds, stone, short and long tons). Carats for gemstones are included as well. Everything runs in your browser.
How the conversion works
Every unit on this page is defined by how many grams it represents. The input is converted to grams, then from grams into the target unit:
result = value × (grams per source unit) ÷ (grams per target unit)
As with length, the imperial factors are exact by definition. The 1959 International Yard and Pound Agreement fixed the pound at exactly 0.45359237 kilograms, so pound-to-kilogram conversions introduce no error of their own.
Weight or mass?
Strictly speaking these are different quantities. Mass is the amount of matter in an object and does not change with location. Weight is the force gravity exerts on that mass, so an object weighs less on the Moon while its mass stays identical.
In everyday use the distinction is ignored, and kilograms and pounds are used for both. That is harmless on Earth, where gravity is near enough constant that the two are proportional. It matters in physics and engineering, where force is measured in newtons rather than kilograms, see the force converter for that case.
Three different tons
"Ton" is one of the most ambiguous units in common use. Three distinct units share the name, and the difference between the largest and smallest is about 12%.
| Unit | Also called | In kilograms | Used in |
|---|---|---|---|
| Metric ton | tonne, t | 1000 kg | Most of the world, international trade |
| Short ton | US ton | 907.18474 kg | United States |
| Long ton | imperial ton | 1016.0469088 kg | Historically UK, shipping |
The short ton is 2000 pounds, the long ton is 2240 pounds, and the metric ton is 1000 kilograms (about 2204.6 pounds). Whenever a figure in tons matters, check which definition applies, especially in freight, mining, and emissions data where the quantities are large enough for the difference to be substantial.
Quick reference table
| From | Grams | Kilograms | Ounces | Pounds |
|---|---|---|---|---|
| 1 mg | 0.001 | 0.000001 | 0.0000353 | 0.0000022 |
| 1 g | 1 | 0.001 | 0.03527 | 0.00220 |
| 1 kg | 1000 | 1 | 35.27396 | 2.20462 |
| 1 oz | 28.34952 | 0.02835 | 1 | 0.0625 |
| 1 lb | 453.59237 | 0.45359 | 16 | 1 |
| 1 stone | 6350.29 | 6.35029 | 224 | 14 |
| 1 metric ton | 1,000,000 | 1000 | 35,274 | 2204.62 |
| 1 carat | 0.2 | 0.0002 | 0.00705 | 0.00044 |
Practical examples
Body weight across countries
Body weight is given in kilograms across most of the world, in pounds in the US, and in stone and pounds in the UK and Ireland. A person at 70 kg weighs 154.3 lb, which a British source would express as 11 stone 0.3 pounds. To convert stone-and-pounds to kilograms, multiply the stone by 6.35029, then add the pounds multiplied by 0.45359.
Luggage allowances
Airlines quote limits in kilograms or pounds depending on the region. A 23 kg checked-bag limit is 50.7 lb, and the common US limit of 50 lb is 22.68 kg. Since these limits are enforced strictly, converting in the direction that rounds against you is the safer habit.
Recipe quantities
Metric recipes give ingredients in grams, US recipes in ounces or cups. One ounce is 28.35 g, and 1 lb is 453.6 g. For dry ingredients, weighing is significantly more accurate than volume measurement, which is why professional baking is done by mass rather than by cup.
Precious metals and gemstones
Gemstones are measured in carats, where 1 carat = 0.2 g exactly, so a 2-carat diamond weighs 0.4 g. Note that the carat used for gemstone mass is a different concept from the karat used for gold purity, where 24 karat means pure gold and 18 karat means 75% gold.
Frequently asked questions
How many pounds is a kilogram?
2.20462 lb. The reverse, 1 lb = 0.45359237 kg, is exact by international definition.
How many pounds is a stone?
Exactly 14 pounds, or 6.35029 kg. The stone is still in everyday use for body weight in the UK and Ireland but is rarely used elsewhere.
Is a US ton the same as a metric ton?
No. A US (short) ton is 907.18 kg, a metric ton is 1000 kg, and a UK (long) ton is 1016.05 kg. The metric ton is about 10% heavier than the US ton.
How many grams is an ounce?
28.34952 g for the standard avoirdupois ounce used for food and general goods. Precious metals use the troy ounce instead, which is 31.1035 g, about 10% heavier.
What is the difference between weight and mass?
Mass is the amount of matter and stays constant everywhere. Weight is the gravitational force on that mass and varies with location. On Earth the two are proportional, which is why the terms are used interchangeably in daily life.
How do I convert kilograms to pounds in my head?
Double the kilograms and add 10%. For 70 kg: 70 × 2 = 140, plus 10% gives 154, and the exact answer is 154.3 lb.
Related converters
- Force converter, for newtons and pound-force where weight is treated as a force
- Volume converter, for recipes that specify volume instead of mass
- All unit converters