How to convert weight units
Choose the unit you have in From and the unit you want in To, enter the value and press Convert. Enter mixed values such as pounds and ounces as a single number first (see the examples below). Negative weights are rejected.
How the conversion works
Every unit is stored as a number of kilograms. The kilogram has been defined since 2019 by a fixed value of the Planck constant rather than by a metal cylinder kept near Paris. The pound is tied to it by the 1959 international yard and pound agreement: one pound is exactly 0.45359237 kg. Everything in the avoirdupois system follows from that. An ounce is 1/16 lb, a stone is 14 lb, and a grain is 1/7,000 lb.
| Mass | Equals |
|---|---|
| 1 pound | 0.45359237 kg |
| 1 ounce | 28.349523125 g |
| 1 stone | 6.35029318 kg |
| 1 short ton (US) | 907.18474 kg |
| 1 long ton (UK) | 1016.0469088 kg |
| 1 troy ounce | 31.1034768 g |
| 1 grain | 64.79891 mg |
| 1 kilogram | ≈ 2.204623 lb |
| 1 gram | ≈ 0.035274 oz |
Strictly speaking, these are units of mass. In physics, weight is the force gravity exerts on a mass and is measured in newtons, but in everyday use "weight" in kilograms or pounds means mass, and that is what this tool converts.
Worked examples
- 70 kg to pounds: 70 ÷ 0.45359237 ≈ 154.32 lb.
- 11 st 4 lb to kilograms: 11 × 14 + 4 = 158 lb, and 158 × 0.45359237 ≈ 71.67 kg.
- 3 lb 8 oz to kilograms: 8 oz is half a pound, so enter 3.5 lb, which is about 1.588 kg.
- 250 g to ounces: 250 ÷ 28.349523125 ≈ 8.82 oz.
Kilograms to pounds
| kg | lb |
|---|---|
| 1 | 2.205 |
| 2 | 4.409 |
| 5 | 11.023 |
| 10 | 22.046 |
| 20 | 44.092 |
| 50 | 110.231 |
| 70 | 154.324 |
| 100 | 220.462 |
Pounds to kilograms
| lb | kg |
|---|---|
| 1 | 0.454 |
| 5 | 2.268 |
| 10 | 4.536 |
| 25 | 11.34 |
| 50 | 22.68 |
| 100 | 45.359 |
| 150 | 68.039 |
| 200 | 90.718 |
Ounces and grams
| oz | g |
|---|---|
| 1 | 28.35 |
| 2 | 56.7 |
| 4 | 113.4 |
| 8 | 226.8 |
| 16 | 453.59 |
| g | oz |
|---|---|
| 10 | 0.35 |
| 50 | 1.76 |
| 100 | 3.53 |
| 250 | 8.82 |
| 500 | 17.64 |
| 1000 | 35.27 |
Units that are easy to confuse
- Three kinds of ton. The metric tonne is 1,000 kg. The US short ton is 2,000 lb (about 907.18 kg) and the UK long ton is 2,240 lb (about 1,016.05 kg). A tonne is about 1.1023 short tons or 0.9842 long tons, so a shipment quoted in "tons" needs to say which.
- Two hundredweights. The US hundredweight is 100 lb and the UK hundredweight is 112 lb. In each system, 20 hundredweights make one ton of that system.
- Troy and avoirdupois ounces. Gold, silver and other precious metals are priced in troy ounces. A troy ounce is 480 grains, about 31.10 g, roughly 9.7% heavier than the everyday ounce of about 28.35 g. The troy pound has only 12 troy ounces, so it is lighter than an ordinary pound: about 373.24 g. A pennyweight is 1/20 of a troy ounce.
- Carat and karat. The metric carat used for gemstones is exactly 200 mg, so 5 carats make a gram. Karat, with a K, describes the purity of gold and is not a unit of mass.
- Grain. The grain is the same size in the avoirdupois and troy systems, about 64.80 mg. It is still used for bullets and arrows.
- Slug and dalton. The slug, about 14.59 kg, is the mass that one pound-force accelerates at one foot per second squared, used in some US engineering work. The dalton is one twelfth of the mass of a carbon-12 atom and is used for molecules and proteins.
Common mistakes
- Multiplying by 2.2. One kilogram is about 2.20462 lb. Rounding to 2.2 makes 100 kg come out as 220 lb instead of about 220.46 lb, an error of about 0.2%.
- Reading decimal pounds as ounces. 7.2 lb is 7 lb 3.2 oz, not 7 lb 2 oz, because a pound has 16 ounces.
- Mixing ounces and fluid ounces. A fluid ounce measures volume, so it only matches a mass once you know the density. Use the volume converter for fluid ounces.
Frequently asked questions
How many pounds are in a kilogram?
About 2.20462. The exact value is 1 ÷ 0.45359237, which does not terminate.
How much is a stone in kilograms?
Exactly 6.35029318 kg, since a stone is 14 lb. Body weight is still often given in stones and pounds in the UK and Ireland.
Is a metric ton the same as a ton?
Not quite. A metric ton (tonne) is 1,000 kg, while the word ton on its own may mean a US short ton of about 907.18 kg or a UK long ton of about 1,016.05 kg.
How many grams are in a troy ounce of gold?
Exactly 31.1034768 g. Ten troy ounces are about 311.03 g, or about 10.97 ordinary ounces.
Supported units
- Tonne (metric ton) (t)
- Kilogram (kg)
- Gram (g)
- Milligram (mg)
- Microgram (µg)
- Pound (lb)
- Ounce (oz)
- Stone (st)
- Short ton (US) (ton (US))
- Long ton (UK) (ton (UK))
- Hundredweight (US) (cwt (US))
- Hundredweight (UK) (cwt (UK))
- Dram (avoirdupois) (dr)
- Grain (gr)
- Troy ounce (oz t)
- Troy pound (lb t)
- Pennyweight (dwt)
- Carat (metric) (ct)
- Slug (slug)
- Dalton (atomic mass unit) (Da)