Weight Converter
The Pound Is Defined by the Kilogram
It surprises people that the imperial pound has no independent physical definition. Since the 1959 international agreement, one avoirdupois pound is exactly 0.45359237 kilograms — a defined constant, not a measured approximation. Every other imperial mass unit cascades from it: an ounce is a sixteenth of a pound, a stone is fourteen pounds, a US short ton is two thousand pounds. That means conversions between metric and imperial mass are exact, and this converter carries the full defined precision rather than the 2.2 lb/kg shorthand.
The Formula
Each unit is stored with one number: its mass in kilograms. Conversions pivot through the kilogram:
(Factors are relative to 1 kilogram)
So 70 kg to stone resolves as 70 × 1.0 ÷ 6.35029318 = 11.02311311 stone. The intermediate value is always in kilograms, which keeps a single rounding step at the end rather than one per hop.
Unit Factors Used by This Converter
| Unit | Code | Kilograms per unit | Definition |
|---|---|---|---|
| Milligrams | mg | 0.000001 | SI submultiple |
| Grams | g | 0.001 | SI submultiple |
| Kilograms | kg | 1 | SI base unit |
| Metric Tons | t | 1000 | 1000 kg |
| Ounces | oz | 0.028349523125 | 1/16 lb |
| Pounds | lb | 0.45359237 | defined exactly |
| Stone | st | 6.35029318 | 14 lb |
| US Tons (Short) | us_ton | 907.18474 | 2000 lb |
| UK Tons (Long) | uk_ton | 1016.0469088 | 2240 lb |
Full Cross-Reference
| 1 of… | Kilograms | Grams | Pounds | Ounces |
|---|---|---|---|---|
| Milligram | 0.000001 | 0.001 | 0.0000022 | 0.00003527 |
| Gram | 0.001 | 1 | 0.00220462 | 0.03527396 |
| Kilogram | 1 | 1000 | 2.20462262 | 35.27396195 |
| Metric Ton | 1000 | 1000000 | 2204.62262185 | 35273.96194958 |
| Ounce | 0.02834952 | 28.34952313 | 0.0625 | 1 |
| Pound | 0.45359237 | 453.59237 | 1 | 16 |
| Stone | 6.35029318 | 6350.29318 | 14 | 224 |
| US Ton (Short) | 907.18474 | 907184.74 | 2000 | 32000 |
| UK Ton (Long) | 1016.0469088 | 1016046.9088 | 2240 | 35840 |
Body Weight: Kilograms, Pounds and Stone
The UK still quotes body mass in stone-and-pounds, the US in pounds, and most of the world in kilograms — the reason this particular conversion gets run so often:
| Kilograms | Pounds | Stone |
|---|---|---|
| 1 kg | 2.20462262 | 0.15747304 |
| 5 kg | 11.02311311 | 0.78736522 |
| 10 kg | 22.04622622 | 1.57473044 |
| 20 kg | 44.09245244 | 3.14946089 |
| 50 kg | 110.23113109 | 7.87365222 |
| 70 kg | 154.32358353 | 11.02311311 |
| 100 kg | 220.46226218 | 15.74730444 |
Situations That Demand the Exact Factor
- Shipping and freight — carriers bill by chargeable weight, and a manifest in pounds against a limit in kilograms needs the full factor. Dividing 2000 lb by a rounded 2.2 gives 909.09 kg; the exact factor gives 907.18474 kg.
- Recipe scaling — converting an ounces-based baking recipe to grams, where a 3–4% error in flour or leavening changes the outcome.
- Gym and barbell loading — matching a kilogram-plated bar to a pound-based programme, or the reverse.
- Materials estimating — aggregate, steel and bulk goods quoted per metric ton against a spec written in short tons.
How to Use This Calculator
- Enter the quantity in the Value field.
- Select what unit that figure is in from the first dropdown.
- Select the unit you want it converted into from the second dropdown.
- Hit Calculate. The output shows the converted mass plus the two factors used, so the arithmetic is auditable.
Related Calculations
For dimensional figures, see the Length Converter; for liquid quantities in recipes and fuel, the Volume Converter covers litres, gallons and cups.