A complete weight and mass converter that handles every common unit at once: milligram, gram, kilogram, tonne, ounce, pound, stone, US (short) ton and imperial (long) ton. Instead of a two-field toy, it gives you a live grid — type a number into any unit and every other field updates instantly from the same underlying mass. There is also a focused from / to line at the top with a swap button for when you just want one direct answer. It is for cooks, shippers, lifters, travellers and anyone juggling metric and imperial weights.
How it works
Every unit is defined relative to a single canonical base: the gram. When you type a value, the tool multiplies it by that unit’s grams-per-unit factor to get the total mass in grams, then divides by each other unit’s factor to express the same mass everywhere else. Because there is one source of truth, the grid can never disagree with itself.
The imperial and US units are all derived from the exact international avoirdupois
pound, fixed in 1959 at 1 lb = 453.59237 g. From that single definition:
1 ounce = 1 lb / 16 = 28.349523125 g(exact)1 stone = 14 lb = 6350.29318 g(exact)1 US ton = 2000 lb = 907184.74 g(exact)1 imperial ton = 2240 lb = 1016046.9088 g(exact)
The metric side is simpler: 1 kg = 1000 g, 1 tonne = 1 000 000 g, 1 mg = 0.001 g.
Results are carried at full floating-point precision and only rounded for display, so
chaining conversions does not accumulate visible error.
Worked example
Suppose you weigh 75 kg and want it in pounds and stones. Type 75 into the kilogram
field. The tool converts to grams (75 times 1000 equals 75,000 g), then divides by the
pound factor: 75000 / 453.59237, giving about 165.35 lb. Dividing instead by the
stone factor gives about 11 st 11.3 lb, or 11.81 stone in decimal. At the same
time the ounce field shows roughly 2,645.5 oz and the tonne field shows 0.075 t —
all from the one number you typed.
Conversion reference
| Unit | Symbol | In grams | In kilograms |
|---|---|---|---|
| Milligram | mg | 0.001 g | 0.000001 kg |
| Gram | g | 1 g | 0.001 kg |
| Kilogram | kg | 1000 g | 1 kg |
| Tonne (metric) | t | 1,000,000 g | 1000 kg |
| Ounce | oz | 28.349523125 g | 0.028349523 kg |
| Pound | lb | 453.59237 g | 0.45359237 kg |
| Stone | st | 6350.29318 g | 6.35029318 kg |
| US ton (short) | US ton | 907,184.74 g | 907.18474 kg |
| Imperial ton (long) | long ton | 1,016,046.9088 g | 1016.0469088 kg |
Quick everyday equivalences: 1 kg is about 2.2046 lb, 1 lb is about 0.4536 kg, 1 stone is 14 lb (about 6.35 kg), and a metric tonne (1000 kg) sits between the US short ton (about 907 kg) and the imperial long ton (about 1016 kg). Every figure is calculated in your browser — nothing is uploaded or stored.