Weight & Mass Converter
Convert between grams, kilograms, ounces, pounds, stones and more — instantly.
This free weight converter switches instantly between metric units (milligrams, grams, kilograms and tonnes) and imperial or US customary units (ounces, pounds, stones and US short tons). Type a value, choose the unit you have and the unit you need, and the answer updates as you type. Below the tool you will find the exact conversion factors, a quick-reference chart, worked examples, and answers to the questions people ask most often when switching between kilograms, pounds and stones.
How the weight converter works
Every unit in the tool is stored as a fixed multiple of one kilogram. When you enter a number, the converter first turns it into kilograms, then divides by the size of the target unit. Because every unit passes through the same base, you can convert between any pair, for example ounces to stones or milligrams to pounds, without needing a separate formula for each combination. Results are rounded to eight significant figures, which is far more precise than any kitchen, bathroom or shipping scale.
The pound used here is the international avoirdupois pound, defined in 1959 as exactly 0.45359237 kg. All other imperial units are built from it: an ounce is one sixteenth of a pound, a stone is 14 pounds, and a US short ton is 2,000 pounds. The UK long ton (2,240 lb) is not the same as the US short ton, and neither is the same as the metric tonne (1,000 kg), which catches many people out when reading shipping or vehicle weights.
Exact conversion factors
| Unit | Equals (kilograms) | Equals (pounds) |
|---|---|---|
| 1 milligram (mg) | 0.000001 kg | 0.0000022 lb |
| 1 gram (g) | 0.001 kg | 0.0022 lb |
| 1 ounce (oz) | 0.0283495 kg | 0.0625 lb |
| 1 pound (lb) | 0.45359237 kg | 1 lb |
| 1 kilogram (kg) | 1 kg | 2.20462 lb |
| 1 stone (st) | 6.35029 kg | 14 lb |
| 1 US short ton | 907.185 kg | 2,000 lb |
| 1 UK long ton | 1,016.05 kg | 2,240 lb |
| 1 metric tonne (t) | 1,000 kg | 2,204.62 lb |
Common weight conversions
| From | To | Result |
|---|---|---|
| 1 kilogram | pounds | 2.205 lb |
| 1 pound | grams | 453.6 g |
| 1 ounce | grams | 28.35 g |
| 100 grams | ounces | 3.527 oz |
| 1 stone | kilograms | 6.350 kg |
| 10 stone | kilograms | 63.50 kg |
| 70 kilograms | stones and pounds | 11 st 0.3 lb |
| 1 tonne | pounds | 2,204.6 lb |
Worked examples
Example 1: kilograms to stones and pounds
In the UK, body weight is usually quoted in stones and pounds, while doctors, gyms and the NHS record it in kilograms. To convert 82 kg:
- Convert to pounds: 82 × 2.20462 = 180.78 lb.
- Divide by 14 to get whole stones: 180.78 ÷ 14 = 12.91, so 12 stone.
- Find the leftover pounds: 180.78 − (12 × 14) = 180.78 − 168 = 12.78 lb.
- Answer: 82 kg is about 12 st 12.8 lb.
Example 2: a recipe in ounces
A US recipe asks for 8 oz of butter. Multiply by 28.3495: 8 × 28.3495 = 226.8 g. A standard UK block of butter is 250 g, so you need just under the whole block. For dry ingredients measured in cups rather than ounces, use our cups to grams guide or the cooking measurement converter, because a cup is a volume and its weight depends on the ingredient.
Example 3: parcel weight for shipping
A courier limit is 30 kg and your parcel weighs 58 lb. Convert pounds to kilograms: 58 × 0.45359 = 26.31 kg, so it is safely under the limit with about 3.7 kg to spare.
Quick mental shortcuts
- Kilograms to pounds: double the number and add 10%. For 50 kg: 100 + 10 = 110 lb (exact answer 110.2 lb).
- Pounds to kilograms: halve the number and subtract 10%. For 200 lb: 100 − 10 = 90 kg (exact answer 90.7 kg).
- Ounces to grams: multiply by 30 and subtract a little. 4 oz is roughly 120 g (exact 113 g).
- Stones to kilograms: multiply by 6.35, or roughly by 6.4 for a fast estimate.
Weight vs mass
In everyday use, “weight” and “mass” mean the same thing, and that is how this converter treats them. In physics, mass is the amount of matter in an object, measured in kilograms, while weight is the force gravity exerts on that mass, measured in newtons. A 10 kg bag has a weight of about 98 N on Earth (10 × 9.81) but only about 16 N on the Moon, even though its mass never changes. Scales show mass because they are calibrated for Earth’s gravity. If you need forces rather than masses, try the physics calculator.
Where each unit is used
Most of the world uses grams and kilograms for everything. The United States uses ounces and pounds for groceries, body weight and shipping, and short tons for vehicles and freight. The United Kingdom is mixed: food is sold in grams and kilograms by law, but many people still describe their body weight in stones and pounds, and road signs for weight limits use tonnes. Medicine and science use milligrams and grams worldwide.
Frequently asked questions
How many pounds are in a kilogram?
One kilogram equals 2.20462 pounds. To go the other way, multiply pounds by 0.45359 to get kilograms.
How many grams are in an ounce?
One avoirdupois ounce is 28.3495 grams. A pound contains 16 ounces, or about 453.6 grams. The troy ounce used for gold and silver is heavier, at 31.1035 grams.
How many kilograms is a stone?
One stone is exactly 14 pounds, which is 6.35029 kilograms.
Is a tonne the same as a ton?
No. A metric tonne is 1,000 kg. A US short ton is 907.2 kg and a UK long ton is 1,016 kg. Always check which one a document means.
Related converters
Need another unit? Try the length converter, the volume converter, or the all-in-one unit converter.