Weight Converter
Convert kilograms, grams, pounds, ounces, and stone with exact factors.
What it does
Weight conversion rests on one exact definition: the international pound is 0.45359237 kilograms, fixed by agreement in 1959. Ounces, stones, and tons all derive from that pound, while grams and kilograms anchor the metric side.
The tool above converts between kilograms, grams, pounds, ounces, and stone. Pick source and target, enter the value, and read the answer with every other unit listed beneath.
Everyday traps cluster around the ounce. Kitchen ounces are 28.35 grams, but fluid ounces measure volume, not weight, and troy ounces for gold run heavier at 31.1 grams. This page converts avoirdupois weight ounces, the kind on food and body scales.
Stone survives mainly in Britain and Ireland for body weight, at 14 pounds each. Kilograms rule everywhere else, including medicine, sport, and science.
How to use
- Enter the value in the source unit.
- Pick source and target units.
- Read the converted line plus all equivalents below it.
- Round once at the end, mainly for cooking where grams beat decimals.
Formula
- 0.45359237
- Kilograms in one international pound, exact by definition.
- 0.028349523125
- Kilograms in one avoirdupois ounce (one sixteenth of a pound).
- 6.35029318
- Kilograms in one stone of 14 pounds.
Going through kilograms keeps one code path for all pairs. The pound factor is exact, so results carry full precision until you choose to round.
Worked example
Example: 150 lb to kilograms
Value 150, from pounds, to kilograms.
- Multiply: 150 x 0.45359237 = 68.0388555 kg.
- Result: 150 lb = 68.0389 kg.
- Check back: 68.0389 / 0.45359237 = 150.00 lb.
- In stone: 150 / 14 = 10.71 st, or 10 st 10 lb.
Reference table
| Pair | Factor | Check |
|---|---|---|
| 1 lb to kg | 0.45359237 | 150 lb is 68.04 kg |
| 1 kg to lb | 2.20462 | 70 kg is 154.32 lb |
| 1 oz to g | 28.3495 | 8 oz is 226.8 g |
| 1 st to kg | 6.35029 | 11 st is 69.85 kg |
| 1 kg to oz | 35.274 | 1 kg is 35.27 oz |
Limits
- Avoirdupois ounces only. Troy ounces for precious metals differ.
- Mass versus weight: scales read mass; conversion holds anywhere on Earth.
- Cooking by volume (cups) needs density, not this converter.
- Tiny jewel weights use grains and carats outside this page.
Common mistakes
- Using 2.2 for lb to kg on medical or freight math where precision counts.
- Reading fluid ounces as weight ounces in recipes.
- Confusing stone with 14 kg. A stone is 14 lb, about 6.35 kg.
- Rounding before a second conversion instead of once at the end.
- Trusting electronic luggage scales past their rated range.
Try it yourself
Quick checks. Answers sit tucked under each question.
80 kg in pounds?
80 / 0.45359237 = 176.37 lb.
500 g in ounces?
0.5 / 0.028349523125 = 17.64 oz.
Questions
How many kg is 1 lb?
Exactly 0.45359237 kg. For everyday use 0.454 is plenty.
How many pounds is 1 kg?
About 2.20462 lb. Double and add ten percent is a fast mental check.
What is a stone in kg?
14 lb, which is 6.35029 kg. Eleven stone is 69.85 kg.
Ounces or fluid ounces?
Weight ounces are 28.35 g of mass. Fluid ounces are 29.57 ml of volume. Recipes mix both.
Why do scales disagree?
Cheap scales drift a percent or two. Weigh twice on hard flat floors for stable numbers.
Grams or kilograms for luggage?
Kilograms with one decimal. Airlines allow 23 kg per bag on many fares.