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Convert kilograms, pounds, grams, ounces, stone and tonnes using exact international definitions — including the troy ounce used for precious metals, and a stone-and-pounds readout for body weight.
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This is the conversion mistake with the largest financial consequences, and most converters do not offer the option at all.
| Avoirdupois ounce | Troy ounce | |
|---|---|---|
| Mass | 28.349523125 g | 31.1034768 g |
| Used for | Food, post, everyday goods | Gold, silver, platinum |
| Ounces per pound | 16 | 12 (in a troy pound) |
| Written as | oz | ozt or "t oz" |
The naming is historical rather than logical. Troy weight comes from the medieval trade fairs at Troyes in France and survived for precious metals because that trade never switched. Avoirdupois — from Old French for "goods of weight" — became standard for everything else.
Australia records body weight in kilograms everywhere official, but stone persists in conversation and American sources use pounds throughout.
| Kilograms | Pounds | Stone & pounds |
|---|---|---|
| 50 kg | 110.2 lb | 7 st 12.2 lb |
| 60 kg | 132.3 lb | 9 st 6.3 lb |
| 70 kg | 154.3 lb | 11 st 0.3 lb |
| 80 kg | 176.4 lb | 12 st 8.4 lb |
| 90 kg | 198.4 lb | 14 st 2.4 lb |
| 100 kg | 220.5 lb | 15 st 10.5 lb |
Freight is where a conversion can be technically correct and still give the wrong answer, because couriers do not necessarily bill by what the scales say.
Carriers charge on whichever is greater — actual or volumetric — because a van fills on space long before it runs out of payload. The divisor varies by carrier and service, with 5000 common for international air freight and 4000 or 6000 also in use, so check before assuming.
| Term | Means |
|---|---|
| Gross weight | Everything — goods, packaging and pallet |
| Net weight | The goods alone |
| Tare weight | Packaging and container alone. Gross minus net |
| Volumetric weight | Derived from the parcel's size, not its mass |
| Chargeable weight | The higher of actual and volumetric — what you pay for |
Australian recipes work in grams, and for baking that is a genuine advantage — weighing flour is far more consistent than scooping it.
| Imperial | Exact metric | Usual rounding |
|---|---|---|
| 1 oz | 28.35 g | 30 g |
| 4 oz | 113.4 g | 115 g or 125 g |
| 8 oz | 226.8 g | 225 g or 250 g |
| 1 lb | 453.6 g | 450 g or 500 g |
| 2 lb | 907.2 g | 900 g or 1 kg |
Weight plates are one of the few places where metric and imperial equipment sit side by side, deliberately close without being equal.
| Equipment | Metric | Imperial | Difference |
|---|---|---|---|
| Olympic barbell | 20 kg | 45 lb = 20.41 kg | 410 g |
| Women's Olympic bar | 15 kg | 35 lb = 15.88 kg | 880 g |
| Large plate | 20 kg | 45 lb = 20.41 kg | 410 g each |
| Medium plate | 10 kg | 25 lb = 11.34 kg | 1.34 kg each |
A "100 kg" lift on metric plates and a "225 lb" lift on imperial plates are 100 kg and 102.06 kg respectively — close enough that people treat them as equivalent, different enough that competition results specify which. Australian gyms are almost entirely metric, so imported programmes written in pounds need converting rather than assuming.
Every conversion on this page in one place — the formula, and the result for a value of one.
| Conversion | Formula | 1 unit gives |
|---|---|---|
| kg → lb | kg × 2.20462262 | 2.2046226 lb |
| lb → kg | lb × 0.45359237 | 0.45359237 kg |
| kg → stone | kg ÷ 6.35029318 | 0.157473 st |
| stone → kg | st × 6.35029318 | 6.35029318 kg |
| g → oz | g ÷ 28.349523125 | 0.0352740 oz |
| oz → g | oz × 28.349523125 | 28.3495231 g |
| troy oz → g | ozt × 31.1034768 | 31.1034768 g |
| kg → troy oz | kg ÷ 0.0311034768 | 32.1507466 ozt |
| tonne → kg | t × 1000 | 1,000 kg |
| lb → oz | lb × 16 | 16 oz |
| stone → lb | st × 14 | 14 lb |
| Unit | In kilograms | Notes |
|---|---|---|
| Microgram (µg) | 0.000000001 | Medication doses, trace analysis |
| Milligram (mg) | 0.000001 | Tablets, nutrition labels |
| Gram (g) | 0.001 | Cooking, small goods |
| Kilogram (kg) | 1 | The SI base unit of mass |
| Tonne (t) | 1,000 | Freight, vehicles, bulk goods |
| Ounce (oz) | 0.028349523125 | Exactly 1/16 pound |
| Troy ounce (ozt) | 0.0311034768 | Precious metals only |
| Pound (lb) | 0.45359237 | Exact by international definition |
| Stone (st) | 6.35029318 | Exactly 14 pounds |
| US short ton | 907.18474 | 2,000 pounds |
| UK long ton | 1,016.0469088 | 2,240 pounds |
How many pounds are in a kilogram?
Exactly 2.2046226 pounds, since the pound is defined as precisely 0.45359237 kilograms. For mental arithmetic, doubling the kilograms and adding 10% gets you very close — 70 kg gives 154 lb, which is right to within a tenth of a pound.
How many kilograms are in a stone?
One stone is 14 pounds, or 6.35029318 kilograms. So 11 stone is about 69.9 kg and 12 stone is about 76.2 kg. Stone is used with pounds as a remainder in speech, which is why this converter shows both the decimal figure and the stone-and-pounds form.
What is a troy ounce and why is it different?
A troy ounce is 31.1034768 grams, about 9.7% heavier than the ordinary avoirdupois ounce of 28.349523125 grams. It is used exclusively for precious metals — gold, silver and platinum are all quoted per troy ounce. Using the wrong one on a 10 oz gold bar puts you out by 27.5 grams.
How many grams are in an ounce?
28.349523125 grams for the standard avoirdupois ounce used in cooking and post. Recipes usually round this to 28 or 30 grams, which is fine for most cooking. For precious metals the relevant unit is the troy ounce at 31.1034768 grams.
Is a pound exactly 0.45359237 kg?
Yes, exactly. Under the international yard and pound agreement of 1959 the pound was defined as precisely 0.45359237 kilograms, making every pound-to-metric conversion exact rather than approximate. The ounce and stone follow from it, at one sixteenth and fourteen pounds respectively.
What is the difference between a tonne and a ton?
A metric tonne is exactly 1,000 kg. A US short ton is 2,000 pounds or about 907 kg, and a UK long ton is 2,240 pounds or about 1,016 kg — a spread of over 10%. Australia uses the metric tonne, so an unqualified "ton" on an imported document is worth checking.
What is volumetric weight?
A figure derived from a parcel's dimensions rather than its mass, used because bulky items fill a vehicle before reaching its payload limit. A common formula is length × width × height in centimetres divided by 5000, so a 40 cm cube counts as 12.8 kg regardless of contents. Carriers bill whichever is higher, actual or volumetric.
What is the difference between gross, net and tare weight?
Net weight is the goods alone. Tare weight is the packaging, pallet or container alone. Gross weight is both together, so gross minus tare equals net. Freight documents specify which is meant, and customs declarations usually want net.
Why does Australia use kilograms?
Australia converted to the metric system during the 1970s, and kilograms have been the legal unit for trade ever since — goods must be sold by metric measure. Stone and pounds survive conversationally for body weight, particularly among older Australians and in imported media, but no official record uses them.
What is the difference between weight and mass?
Mass is how much matter something contains, measured in kilograms, and it is the same everywhere. Weight is the force gravity exerts on it, measured in newtons, and it changes with location. This converter handles mass, which is what people mean in everyday use. Our weight and force calculator covers the physics distinction in detail.
Are Olympic weight plates the same in kg and lb?
Close, but not identical. An Olympic barbell is 20 kg while an American bar is 45 lb, which is 20.41 kg, and the large plates follow the same pattern. A 100 kg lift and a 225 lb lift differ by about 2 kg, which is why competition results specify the unit rather than treating them as equivalent.
What is the SI unit of mass?
The kilogram — unusual among SI base units in that its name includes a prefix. Since 2019 it has been defined through the Planck constant rather than a physical prototype, so it can be realised in any properly equipped laboratory rather than depending on one metal cylinder in France.
The maths here is exact — the pound is a defined multiple of the kilogram, so nothing is approximated. What causes trouble is the units themselves: an "ounce" means two different masses, a "ton" means three, and a parcel's billable weight may bear no relation to what the scales read.
When a conversion matters financially, check which unit the source actually meant before converting it.
For other measurement types, the unit converter covers ten categories, and the weight and force calculator handles mass versus weight and gravity on other planets.