Convert lb to kg and kg to lb using the international avoirdupois pound — defined since 1959 as exactly 0.45359237 kg. Includes lb + oz, kg to lb + oz, stone, step-by-step working, and a table of common body-weight and shipping values.
kg = lb × 0.45359237lb = kg ÷ 0.453592370.45359237 kg2.20462262 lbConvert pounds and kilograms
Instant free online pound to kilogram converterwith five advanced input modes
Pick the pair you already have. Every route returns the full answer plus the substituted working.
Pounds to kilograms — common values
body weight and shippingThese are the values people search for most often. The middle column uses the exact factor; the right column shows the rounded value you'll see on most scales and forms.
| Pounds (lb) | Kilograms (exact) | Kilograms (rounded) |
|---|---|---|
| 1 lb | 0.45359237 kg | 0.45 kg |
| 5 lb | 2.26796185 kg | 2.27 kg |
| 10 lb | 4.53592370 kg | 4.54 kg |
| 20 lb | 9.07184740 kg | 9.07 kg |
| 50 lb | 22.6796185 kg | 22.68 kg |
| 100 lb | 45.3592370 kg | 45.36 kg |
| 120 lb | 54.4310844 kg | 54.43 kg |
| 150 lb | 68.0388555 kg | 68.04 kg |
| 180 lb | 81.6466266 kg | 81.65 kg |
| 200 lb | 90.7184740 kg | 90.72 kg |
| 250 lb | 113.3980925 kg | 113.40 kg |
| 300 lb | 136.0777110 kg | 136.08 kg |
The “exact” column is the product of the pound value and 0.45359237. The “rounded” column is the same number cut to two decimal places — the value most scales display.
Kilograms to pounds — common values
the reverse directionFor the same values in the opposite direction. Note that 1 kg is not a clean number of pounds — it is 2.20462262…, a repeating decimal.
| Kilograms (kg) | Pounds (exact) | Pounds (rounded) |
|---|---|---|
| 1 kg | 2.20462262 lb | 2.20 lb |
| 5 kg | 11.0231131 lb | 11.02 lb |
| 10 kg | 22.0462262 lb | 22.05 lb |
| 20 kg | 44.0924524 lb | 44.09 lb |
| 50 kg | 110.231131 lb | 110.23 lb |
| 70 kg | 154.323584 lb | 154.32 lb |
| 80 kg | 176.369810 lb | 176.37 lb |
| 100 kg | 220.462262 lb | 220.46 lb |
Worked examples
four routes, four answersEach shows the substituted numbers so you can follow by hand or verify the converter output. Check out detailed guide on how to convert lbs to kg with accuracy.
150 lb to kg
150 lb, international avoirdupois
kg = 150 × 0.45359237 = 68.0388555. Rounded to two decimals: 68.04 kg.
Answer: 68.04 kg
70 kg to lb
70 kg, SI kilograms
lb = 70 ÷ 0.45359237 = 154.323584. Rounded to one decimal: 154.3 lb.
Answer: 154.32 lb
11 st 4 lb to kg
11 stone 4 pounds, UK body weight
11 st × 14 = 154 lb, plus 4 lb = 158 lb total. kg = 158 × 0.45359237 = 71.6676. Rounded: 71.67 kg.
Answer: 71.67 kg
5 lb 8 oz to kg
5 pounds 8 ounces, US birth weight
8 oz ÷ 16 = 0.5 lb, so total = 5.5 lb. kg = 5.5 × 0.45359237 = 2.494758. Rounded: 2.49 kg.
Answer: 2.49 kg
Frequently asked questions
12 answers, mapped to real searchesTap any question to expand the answer.
What is the exact conversion factor from pounds to kilograms?
Since the 1959 International Yard and Pound Agreement, the international avoirdupois pound is defined as exactly 0.45359237 kilograms. This is not a rounded value — it is the legal definition used by NIST and every national metrology institute. The reverse is 1 kg = 2.2046226218… lb, which is a repeating decimal.
How do I convert pounds to kilograms step by step?
Multiply the number of pounds by 0.45359237. For 180 lb: 180 × 0.45359237 = 81.6466266. Round to the precision you need — 81.65 kg for two decimals, 81.6 kg for one, or 82 kg for a rough estimate. The same formula works for any pound value, including fractional ounces after you convert ounces to a fraction of a pound (divide by 16).
How do I convert kilograms to pounds step by step?
Divide the number of kilograms by 0.45359237, or equivalently multiply by 2.20462262. For 75 kg: 75 ÷ 0.45359237 = 165.3467. Rounded: 165.35 lb. The two operations give the same result because they are inverses of each other.
Why is 1 kg not exactly 2.2 lb?
Because 2.2 is a convenient approximation, not the exact value. The exact reciprocal of 0.45359237 is 2.2046226218…, a repeating decimal. Using 2.2 introduces an error of about 0.21% — small for a suitcase, but noticeable for a 100 kg shipment (2.2 gives 220 lb, exact gives 220.46 lb). For anything where precision matters, use the full factor.
Is a pound a unit of mass or weight?
Technically, the avoirdupois pound is a unit of mass, not weight. In everyday speech people say “weight,” but the pound measures how much matter is in an object, the same quantity the kilogram measures. Weight is a force (mass × gravity), measured in newtons or pound-force. This page converts mass to mass, which is what almost every use case actually needs.
How do I convert stone and pounds to kilograms?
One stone is 14 pounds. Multiply the stone value by 14, add the remaining pounds, then multiply by 0.45359237. For 11 st 4 lb: (11 × 14) + 4 = 158 lb, then 158 × 0.45359237 = 71.67 kg. The converter above has a dedicated stone + lb mode that does both steps.
How do I convert pounds and ounces to kilograms?
Divide the ounces by 16 to get a fraction of a pound, add the whole pounds, then multiply by 0.45359237. For 7 lb 8 oz: 8 ÷ 16 = 0.5, so 7.5 lb, then 7.5 × 0.45359237 = 3.40 kg. This is the standard route for birth weights and small packages.
What is the difference between lb and lbs?
Nothing — both mean pound. lb is the singular abbreviation (from the Latin libra), and lbs is the informal plural. In scientific and legal writing, lb is used for both singular and plural. You will also see lbm (pound-mass) to distinguish it from lbf (pound-force).
How many pounds are in a kilogram?
One kilogram is 2.2046226218 pounds, a repeating decimal. For everyday use, 2.2 lb is close enough. For a 70 kg person: exact is 154.3236 lb, 2.2 gives 154 lb — a difference of about 0.32 lb (145 grams).
How many kilograms are in a pound?
One pound is exactly 0.45359237 kilograms. This is a finite decimal, not a repeating one, because the pound is defined in terms of the kilogram. A 150 lb person is 68.0388555 kg, or 68.04 kg rounded.
Can I use this converter for shipping and freight?
Yes, for mass conversion. But note that freight often uses dimensional weight (volume ÷ a dim factor) rather than actual weight, and that is a different calculation. This page converts the actual mass. For volumetric weight, use a dedicated dim-weight calculator, and confirm the carrier's divisor (typically 139 for inches/lb or 5000 for cm/kg).
How accurate is the converter?
The converter uses the exact 0.45359237 factor in full double-precision floating point. Displayed results are rounded to four decimal places, which is enough for body weight, shipping, cooking and most engineering. For legal-for-trade weighing, use a certified scale and the exact factor; do not rely on a web tool for compliance.