About Weight Converter
Convert between mg, g, kg, oz, lb, stones, and metric tons. Free, no sign-up required.
How to use
- Type your weight or mass into the Value field. Decimals are accepted, so 68.5 kg or 2.25 lb both work and the result updates the moment you finish typing.
- Pick the source unit from the From dropdown. Available: milligrams (mg), grams (g), kilograms (kg), ounces (oz), pounds (lb), stones (st), and metric tons (t).
- Choose the target unit in the To dropdown. The default pairing is kilograms to pounds; switch to oz-to-g for cooking precision, mg-to-g for dosing, or stones-to-kg for UK personal weight.
- Use the swap button between the dropdowns to instantly reverse the conversion. The result and the formula line update together — handy when you want to verify a factor by running it both ways.
- Below the highlighted result you will see the explicit formula (e.g. '5 lb = 2.267961 kg'). Use this for anything that needs documentation: spec sheets, lab notes, or homework where you have to show your work.
- All conversions in this tool refer to mass, not weight in the strict physics sense. Mass is constant; weight (force from gravity) varies with location. In everyday Earth-surface use the two are interchangeable, but for orbital mechanics or precision physics, multiply mass by local g (≈9.81 m/s² at sea level) to get weight in newtons.
Examples
Personal weight
150 lb equals 68.04 kg or 10 stones 10 lb (UK still commonly uses stones for body weight). The kg-to-lb factor 2.20462 is one of the most-memorized conversions in fitness, medicine, and travel — divide by 2.2 for a quick mental estimate.
Cooking precision
1 oz equals 28.35 g — a useful reference because most digital kitchen scales toggle between g and oz. 1 lb = 16 oz = 453.59 g. For baking by weight, professionals work in grams: tighter tolerances and easier scaling than imperial fractions.
Industrial scale
1 metric ton (1,000 kg) = 2,204.62 lb = 1.1023 US short tons. The US short ton is 2,000 lb (907.185 kg), and the UK long ton is 2,240 lb (1,016.05 kg). Three different 'tons' in active use — always verify which one a freight quote or commodity price refers to.
Frequently asked questions
How do I convert pounds to kilograms?
Divide pounds by 2.20462, or equivalently multiply by 0.453592, to get kilograms. So 150 lb / 2.20462 ≈ 68.04 kg. Quick mental shortcut: divide pounds by 2.2 (gives you about 1% high — fine for everyday estimates). The factor 0.45359237 is exact by international agreement (1959 international yard and pound), so the conversion has no fundamental rounding error.
What is the difference between mass and weight?
Mass measures the amount of matter in an object — measured in kilograms, grams, or pounds-mass, and constant everywhere in the universe. Weight measures the gravitational force on that mass — measured in newtons (or pounds-force) and varies with local gravity. You weigh roughly 1/6 as much on the Moon, but your mass is unchanged. In everyday English we use 'weight' to mean 'mass,' and at Earth's surface (where g is constant within ±0.5%) the distinction usually does not matter.
How many grams are in an ounce?
1 avoirdupois ounce (the everyday US ounce, used for food, packages, body weight) = 28.3495 g. 1 troy ounce (used for precious metals: gold, silver, platinum) = 31.1035 g — about 9.7% heavier. So a 1 oz gold coin is heavier than a 1 oz steak. Always check which ounce a price or weight references; precious-metal markets default to troy. This converter uses avoirdupois.
What is a stone and where is it used?
1 stone (st) = 14 lb = 6.35029 kg. It is still the dominant unit for personal body weight in the UK and Ireland (e.g. '10 stone 6' for 146 lb / 66.2 kg). British medical records, fitness apps, and casual conversation use it; the rest of the world uses kg or lb. Stones are sometimes also used in equestrian and butchery contexts. Outside those niches, the stone is gradually disappearing in favor of kilograms.
What is the difference between a metric ton, a short ton, and a long ton?
Metric ton (tonne, t) = 1,000 kg = 2,204.62 lb — the international standard. US short ton = 2,000 lb = 907.185 kg — used in US shipping, mining, and bulk commodities. UK long ton = 2,240 lb = 1,016.05 kg — historical UK unit, still seen in some shipping contexts. Differences are not trivial: a freight quote of '100 tons' could mean 90,718 kg, 100,000 kg, or 101,605 kg depending on the unit. This converter uses metric tons; multiply or divide accordingly for short/long.
Why is gold weighed in troy ounces?
The troy system dates to medieval European trade fairs (Troyes, France) and survived into modern precious-metal markets. 1 troy ounce = 480 grains = 31.1035 g. The avoirdupois ounce used for groceries is 437.5 grains = 28.3495 g — about 9.7% lighter. Troy weights survive only for precious metals (gold, silver, platinum, palladium) and gemstones. Every other commercial weight in the US is avoirdupois.
How is the kilogram defined?
Since May 2019, the kilogram is defined by fixing the Planck constant at exactly 6.62607015 × 10⁻³⁴ J·s. Before that, the kg was defined by a physical platinum-iridium cylinder kept in Paris (the IPK or 'Le Grand K') from 1889 to 2019 — the last SI base unit defined by an artifact. The Planck-based definition is realized in practice using a Kibble balance, which equates electrical and mechanical power to derive mass.
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