# How do I convert a weight?

Converts a weight from any unit to any other: milligrams, grams, kilograms, tons, ounces, pounds, stone, and grains.

- Page: https://www.acalculator.org/convert/weight
- JSON spec: https://www.acalculator.org/convert/weight.json
- Version: e01fb97b18d7

## Default answer

Example with the default inputs (Weight 150, From pounds (lb), To kilograms (kg)): 150 pounds (lb) = 68.038856 kilograms (kg).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| amount | Weight | The weight to convert, in the "From" unit. |
| from | From | The unit the weight is in. |
| to | To | The unit to convert the weight to. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| result | Converted weight | The weight in the "To" unit. |
| kg | Kilograms (kg) | The weight in kilograms. |
| g | Grams (g) | The weight in grams. |
| lb | Pounds (lb) | The weight in pounds. |
| oz | Ounces (oz) | The weight in avoirdupois ounces. |
| lbOz | Pounds and ounces | Whole pounds and the ounces left over, to 0.01 oz. |
| stLb | Stone and pounds | Whole stone and the pounds left over, to 0.01 lb. |

## Method

converted = weight × (kilograms per "From" unit) ÷ (kilograms per "To" unit)

## Assumptions

- Kilograms per unit come from the exact definitions in NIST SP 811: 1 lb = 0.45359237 kg, 1 oz = 1/16 lb, 1 grain = 1/7,000 lb, 1 US short ton = 2,000 lb, 1 metric ton = 1,000 kg, 1 UK long ton = 2,240 lb.
- 1 stone = 14 lb (UK Weights and Measures Act 1985).
- Ounces are avoirdupois ounces, the ounces of weight. Troy ounces (for precious metals) are a different unit.
- The answer shows at most 6 decimal places; the calculation keeps full precision.

## Worked examples

1. amount = 150, from = lb, to = kg gives result = 68.038856, lb = 150, lbOz = 150 lb 0 oz, stLb = 10 st 10 lb. Source: NIST SP 811 (2008) B.8: 1 lb = 0.45359237 kg exactly.
2. amount = 1, from = kg, to = lb gives result = 2.204623, oz = 35.273962, lbOz = 2 lb 3.27 oz, stLb = 0 st 2.2 lb. Source: NIST SP 811 (2008) B.8: 1 kg = 1 ÷ 0.45359237 lb.
3. amount = 10, from = st, to = kg gives result = 63.502932. Source: UK Weights and Measures Act 1985, Schedule 1: 1 stone = 14 lb.
4. amount = 1, from = lton, to = t gives result = 1.016047. Source: NIST SP 811 (2008) B.8: 1 long ton = 2,240 lb = 1,016.0469088 kg.
5. amount = 1, from = ton, to = lb gives result = 2,000. Source: NIST SP 811 (2008) B.8: 1 short ton = 2,000 lb.

## FAQ

### How many kilograms are in a pound?

1 pound is exactly 0.45359237 kg, by the international definition of 1959 (NIST SP 811). So 150 lb is 150 × 0.45359237 = 68.0388555 kg.

### How many pounds are in a stone?

14. A stone is 14 lb (UK Weights and Measures Act 1985), which is 6.35029318 kg. 10 st 10 lb is 150 lb.

### What is the difference between a short ton, a metric ton, and a long ton?

A US short ton is 2,000 lb (907.18474 kg), a metric ton or tonne is 1,000 kg, and a UK long ton is 2,240 lb (1,016.0469088 kg). In the US, "ton" means the short ton.

### Is weight the same as mass?

In everyday use, yes. Scales show mass in kilograms or pounds, and this calculator converts between those units. In physics, weight is a force measured in newtons, which depends on gravity.

### Is an ounce of gold the same as an ounce here?

No. This calculator uses the avoirdupois ounce, 1/16 lb (28.349523125 g). Gold and silver are weighed in troy ounces of 31.1034768 g.

## Sources

- NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B.8: pound, ounce, grain, short ton, long ton, metric ton. https://www.nist.gov/pml/special-publication-811
- UK Weights and Measures Act 1985, Schedule 1, Part VI: 1 stone = 14 pounds. https://www.legislation.gov.uk/ukpga/1985/72/schedule/1