Converters
Weight & Mass Converter
Convert between kilograms, grams, pounds, ounces, stone, and tons with exact definitions — all units displayed simultaneously.
| Milligrams (mg) | 1 |
| Grams (g) | 0.001 |
| Kilograms (kg) | 0.000001 |
| Metric tons (t) | 0 |
| Ounces (oz) | 0.000035 |
| Pounds (lb) | 0.000002 |
| Stone (st) | 0 |
| US tons (short) | 0 |
Anchored conversions from Milligrams (mg) use exact internationally agreed factors. Everything is computed locally, instantly.
Weight, Mass and the Exceptions That Trip People Up
Strictly, kilograms measure mass and pounds, as used on scales, measure weight (force). The converter uses the standard convention that treats them as equivalent at Earth surface gravity — which is correct for every everyday purpose, including cooking, shipping and gym work.
Two cases genuinely surprise people: precious metals are traded in troy ounces (31.103 g, not 28.35 g — a 10% difference you do not want to discover after a sale), and carat, for gemstones, is 200 mg regardless of the stone. Both units are deliberately excluded from general-purpose conversions because mixing them in is how errors happen.
Exact factors, and where rounding happens
Only a handful of factors are exact by definition: 1 lb = 0.45359237 kg (international avoirdupois pound), 1 oz = 1/16 lb, 1 st = 14 lb, and 1 t = 1000 kg. Everything else — pounds to kilograms, kilograms to stone — is a ratio derived from those definitions, so the same input always produces the same output.
Rounding is applied only for display. The calculation keeps full precision internally and shows two decimals, which is more than enough for any real-world measurement: a bathroom scale reads to about 0.1 kg, and a parcel service to about 50 g. If you need a value at full precision for a recipe or engineering sheet, take the factor itself (for example 0.45359237) rather than a rounded result.
Quick reference: common weight conversions
| From | To | Exact / standard factor |
|---|---|---|
| 1 kg | lb | 2.204622 |
| 1 lb | kg | 0.45359237 (exact) |
| 1 oz | g | 28.349523125 (exact) |
| 1 st | kg | 6.35029318 (exact) |
| 1 t (metric) | lb | 2204.62262 |
| 1 US ton | kg | 907.18474 (exact) |
Derived from the definitions above; the converter rounds only the displayed result, never the calculation.
How the Conversion Works
- Enter a value and choose the source unit.
- Every other unit converts at once: mg, g, kg, t, oz, lb, st, and US ton.
- Pounds use the exact definition 1 lb = 0.45359237 kg.
- Stone results also show the classic st + lb split used in the UK.
Conversion Example
Common Questions
Is weight the same as mass?
Strictly, mass is the amount of matter (kg) and weight is the gravitational force on it (newtons). Everyday converters treat them as equivalent at Earth’s surface gravity.
What is the difference between a metric ton and US ton?
A metric ton is 1000 kg. The US "short ton" is 2000 lb (≈907.18 kg). Both are listed so mixed-source data converts correctly.
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