What this tool does
Weight conversions appear in three places that all matter: body weight on a fitness app, parcel limits at a shipping counter, and product weights on a label printed for another market. The two systems differ by more than a factor of two between their base units, so a rough multiplier drifts quickly. This converter uses the exact international pound and includes the stone, and it accepts a value from either system without any pre-converting.
How it works
The kilogram is the SI base unit of mass, and the rest of the metric column is a prefix of it: one gram is a thousandth of a kilogram and one metric tonne is a thousand kilograms. The imperial side has no such ladder. Pounds and ounces relate by sixteen, stones relate to pounds by fourteen, and there is no single ratio that connects the two families together.
The connection is one exact number: one pound is 0.45359237 kilograms, fixed by international agreement in 1959. Everything else follows from it. Kilograms to pounds multiply by 2.20462262, pounds to kilograms multiply by 0.45359237, and one ounce is exactly 28.349523125 grams. Because the factor is exact, the only rounding in a result comes from where you stop the decimals, not from the conversion.
The stone is the case people get wrong. It is 14 pounds, or 6.35029318 kilograms, and it remains the normal way body weight is stated in the UK and Ireland even though most scales elsewhere display kilograms or pounds. Converting through it as an intermediate step would add an unnecessary rounding, so the tool converts from the base unit in one pass and reports the stone figure alongside the pounds.
Worked example
Converting 70 kg to pounds and to stone.
- 70 × 2.20462262 = 154.3236 lb
- 70 ÷ 6.35029318 = 11.0231 stone
- 11 stone = 154 lb, remainder 0.3236 lb = 5.18 oz
70 kg = 154.32 lb = 11 stone 0.32 lb. One kilogram is 2.20462 lb, so 1 kg = 2.20 lb.
Accuracy and limitations
- Scales measure mass and report it in weight units, so these conversions are mass to mass; in a changing gravitational field, weight in newtons would need a separate calculation.
- Avoirdupois pounds and ounces are used here. Troy ounces, used for precious metals, are 31.1035 g rather than 28.3495 g.
- For trade, pharmacy or legal measurement, use the official standard for your jurisdiction.
Frequently asked questions
- How many pounds are in a kilogram?
- 2.20462 pounds, from the exact factor 1 lb = 0.45359237 kg. Rounded for everyday use, 1 kg is 2.20 lb, which is the number most fitness and shipping references quote.
- How do I convert kg to lbs?
- Multiply by 2.20462. 70 kg × 2.20462 = 154.32 lb, which is why 70 kg in pounds is almost always quoted as 154 lb.
- How many grams are in an ounce?
- 28.3495 grams exactly, since one pound is 453.59237 g and contains 16 ounces. For cooking, 28.35 g per ounce is accurate to well under a tenth of a gram.
- How many pounds are in a stone?
- Fourteen pounds, which is 6.35029318 kg. So 70 kg is 154.32 lb, or 11 stone 0.32 lb, and a person of 11 stone weighs exactly 154 lb.
- Is 70 kg 154 or 155 pounds?
- 154.32 pounds, so it rounds to 154 lb. The exact product is 70 × 2.20462262 = 154.3236, and rounding up to 155 would overstate the weight by about 0.7 lb.
- What is 1 kg in pounds and ounces?
- 1 kg = 2.20462 lb, which is 2 lb 3.27 oz. The ounces are the fractional part, 0.20462 × 16 = 3.27, once the whole pounds are removed.