About the Weight / Mass Converter
This converts a weight (strictly, a mass) between metric and imperial units — for body weight in kilograms, pounds or stone, recipe and postage weights in grams and ounces, or shipping weights in tonnes and tons. Choose the units and enter a value for an instant result, with a swap button to reverse the direction.
How it works
Each unit has an exact factor relative to the kilogram, so your value is converted to kilograms and then to the target unit. The definitions used are exact:
- 1 pound = 0.45359237 kg, and 1 ounce = 1⁄16 pound (28.3495 g).
- 1 stone = 14 pounds (6.35 kg).
- 1 tonne (metric) = 1000 kg.
- 1 US short ton = 2000 lb (907.18 kg); 1 Imperial long ton = 2240 lb (1016.05 kg).
Ounces and pounds here are the everyday avoirdupois units, not the troy ounces used for precious metals.
Assumptions and behaviour
- Mass vs weight: kilograms and pounds measure mass. In everyday use on Earth they're used as weight, which is what this tool assumes; strictly, true weight (a force) also depends on gravity.
- Ounces are avoirdupois (1⁄16 lb), not troy ounces (used for gold and silver, which are heavier).
- US ton ≠ Imperial ton ≠ tonne — the three are different; pick carefully.
- Results show about 7 significant figures.
Limitations
- Precious-metal (troy) weights aren't included. A troy ounce (~31.1 g) is heavier than the avoirdupois ounce here (~28.35 g), so don't use this for gold, silver or gemstone weights.
- It converts mass units only; it can't turn a volume (like a cup or litre) into a weight — that needs the substance's density.
- Displayed values are rounded, so hand-chaining rounded figures can drift slightly.
Privacy
The conversion runs entirely in your browser. Nothing is uploaded or stored.
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