# Weight and mass converter

> Enter a weight in any unit and get the equivalent in all others — metric, imperial, and avoirdupois.

Convert between grams, kilograms, pounds, ounces, stone, metric tons, and US and long tons instantly.

**Interactive version:** https://onlinecalculator.me/unit-converters/weight-mass/
**Category:** Unit Converters

## How it works

The converter uses gram as the base unit. Every input unit is first converted to grams using its exact definition, then the result is divided by the target unit's gram equivalent.

For example, 1 kilogram = 1,000 grams; 1 pound = 453.59237 grams (the exact NIST definition). So 5 kg = 5,000 g ÷ 453.59237 = 11.0231 lb.

## Unit reference

| Unit | Symbol | Exact gram equivalent |
|------|--------|-----------------------|
| Milligram | mg | 0.001 g |
| Gram | g | 1 g |
| Kilogram | kg | 1,000 g |
| Metric ton | t | 1,000,000 g |
| Ounce (av.) | oz | 28.349523125 g |
| Pound (av.) | lb | 453.59237 g |
| Stone | st | 6,350.29318 g |
| US short ton | ton | 907,184.74 g |
| Long ton | lt | 1,016,046.909 g |

## Worked examples

### Body weight — 150 lb

- 150 × 453.59237 = 68,038.86 g = **68.04 kg**
- 150 ÷ 14 = **10.71 stone** *(10 st 10 lb)*
- 150 × 16 = **2,400 oz**

### Shipping — a 5 kg package

- 5 × 1,000 = 5,000 g
- 5,000 ÷ 453.59237 = **11.02 lb**
- 11.02 × 16 = **176.37 oz**
- In metric tons: **0.005 t**

### Industrial scale — 1 metric ton of cargo

- 1 tonne = **2,204.62 lb**
- 1 tonne = **1.1023 US short tons**
- 1 tonne = **0.9842 long tons** *(UK)*

## Notes

- **"Weight" vs. "mass"** — in everyday use they're interchangeable, but physically mass is the amount of matter (kg), and weight is the force gravity exerts on it (newtons). On the Moon your mass is the same but you weigh about 1/6 as much. All the units here are mass units despite the label.
- **Three kinds of "ton"** — US short ton (2,000 lb), long ton (2,240 lb, still common in UK), metric ton / tonne (1,000 kg ≈ 2,205 lb). They differ by up to 12%, which matters for shipping quotes and freight rates.
- **Avoirdupois vs. troy** — the ounces and pounds above are avoirdupois (everyday use). Troy ounces, used for precious metals, are different: 1 troy oz = 31.1 g (heavier than a regular ounce). A "pound of gold" at the jeweler's is not the same as a pound of flour.
- Conversion factors follow NIST definitions; 1 lb = 453.59237 g exactly.

## Frequently asked questions

### How many pounds in a kilogram?

One kilogram equals approximately 2.20462 pounds. This is the exact conversion used by the NIST.

### What is a stone in kilograms?

One stone is exactly 14 pounds, which equals approximately 6.35029 kilograms. Stone is used mainly in the UK and Ireland for body weight.

### How many ounces in a pound?

Exactly 16 avoirdupois ounces in one pound.

### What is the difference between a metric ton and a US ton?

A metric ton (tonne) is 1,000 kg (2,204.6 lb). A US short ton is 2,000 lb (907.2 kg). A long ton (UK) is 2,240 lb (1,016 kg).

### How do I share my conversion?

Click "Share with my numbers" to copy a URL that restores your exact value and units when opened.

## Sources

- [Kilogram — SI base unit of mass](https://en.wikipedia.org/wiki/Kilogram) — Wikipedia
- [Pound (mass) — avoirdupois pound and kilogram conversion](https://en.wikipedia.org/wiki/Pound_(mass)) — Wikipedia
- [NIST Special Publication 811: Guide for the Use of the SI (conversion factors)](https://www.nist.gov/pml/special-publication-811) — National Institute of Standards and Technology

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