How the weight converter works
This weight converter changes a mass from one unit to another: kilograms, grams, milligrams, metric tons, pounds and ounces. Type a number, choose the From and To units, and press Convert. Every value passes through the kilogram using exact factors, so nothing is rounded until the final displayed result.
The answer is shown to at most 8 decimal places with trailing zeros removed. That's plenty for everyday use, but it means a very small result can display as 0: one milligram is 0.000000001 metric tons, which is past the eighth decimal place. If you see a 0 you didn't expect, convert to a smaller unit. The Swap button exchanges the From and To units; press Convert again to recalculate.
Exact conversion factors
| Unit | Symbol | In kilograms |
|---|---|---|
| Metric ton | t | 1,000 |
| Kilogram | kg | 1 |
| Gram | g | 0.001 |
| Milligram | mg | 0.000001 |
| Pound | lb | 0.45359237 |
| Ounce | oz | 0.028349523125 |
The metric units are powers of ten apart. The pound has been defined as exactly 0.45359237 kg since the 1959 international yard and pound agreement, and the ounce is one sixteenth of that, which is why its factor ends in a long but exact string of digits. Both values are listed in NIST Special Publication 811, the US guide to SI units.
The kilogram itself has been defined since 2019 by fixing the numerical value of the Planck constant, replacing the platinum-iridium cylinder kept near Paris. The BIPM SI Brochure sets out the current definition. For converting kitchen or body weights none of this changes anything, but it's the reason the factors above are exact rather than measured.
Quick reference
| From | To | Multiply by |
|---|---|---|
| kilograms | pounds | 2.20462 |
| pounds | kilograms | 0.45359237 |
| ounces | grams | 28.3495 |
| grams | ounces | 0.035274 |
| pounds | ounces | 16 |
| metric tons | pounds | 2,204.62 |
Worked examples
These are the results the converter returns, rounded for readability where noted.
- Body weight, 80 kg in pounds: 80 ÷ 0.45359237 = 176.37 lb.
- A 5 lb bag of flour in kilograms: 5 × 0.45359237 = 2.268 kg.
- A 12 oz steak in grams: 12 × 28.349523125 = 340.19 g.
- A 100 g chocolate bar in ounces: 3.527 oz.
- One pound in ounces: exactly 16 oz, a good sanity check that the two imperial factors agree.
Units that aren't in this converter
A few common weight units aren't listed, but you can still get there in two steps:
- Stone (UK body weight) is 14 lb. For 11 st 4 lb, work out 11 × 14 + 4 = 158 lb, then convert: 158 lb = 71.67 kg.
- Troy ounce (gold, silver) is 31.1034768 g. Enter the grams instead.
- Short and long tons are 2,000 lb and 2,240 lb. Enter the pounds and convert to metric tons or kilograms.
- Carat (gemstones) is exactly 200 mg, so a 1.5-carat stone is 300 mg.
Mass, weight and scales
A bathroom scale actually measures the force you press down with and divides by an assumed value of gravity to show kilograms or pounds. Gravity varies slightly with latitude and altitude, so in strict physics terms your "weight" changes a little from place to place while your mass doesn't. For anything that needs force units, such as load ratings, use the force converter.
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