Pounds to Kilograms Converter
Convert lbs to kg (or kg to lbs) using the exact factor, with the answer also shown as kilograms and grams or pounds and ounces.
kg = lb × 0.45359237
Pounds to Kilograms Chart
Rounded to two decimal places. The 100–200 lb rows cover most adult body weights.
| Pounds | Kilograms | kg and g |
|---|---|---|
| 1 lb | 0.45 | 0 kg 454 g |
| 5 lb | 2.27 | 2 kg 268 g |
| 10 lb | 4.54 | 4 kg 536 g |
| 25 lb | 11.34 | 11 kg 340 g |
| 50 lb | 22.68 | 22 kg 680 g |
| 100 lb | 45.36 | 45 kg 359 g |
| 110 lb | 49.9 | 49 kg 895 g |
| 120 lb | 54.43 | 54 kg 431 g |
| 130 lb | 58.97 | 58 kg 967 g |
| 140 lb | 63.5 | 63 kg 503 g |
| 150 lb | 68.04 | 68 kg 39 g |
| 160 lb | 72.57 | 72 kg 575 g |
| 170 lb | 77.11 | 77 kg 111 g |
| 180 lb | 81.65 | 81 kg 647 g |
| 190 lb | 86.18 | 86 kg 183 g |
| 200 lb | 90.72 | 90 kg 718 g |
| 220 lb | 99.79 | 99 kg 790 g |
| 250 lb | 113.4 | 113 kg 398 g |
| 300 lb | 136.08 | 136 kg 78 g |
Worked Example: Body Weight and BMI in kg
A doctor's form abroad asks for weight in kilograms, and you know yours as 185 lb at 5 ft 10 in. Here is the conversion, and a check that BMI comes out the same either way.
Step 1: Pounds to kilograms
Step 2: Height in metres
Step 3: Metric BMI (kg ÷ m²)
Check: US BMI formula (703 × lb ÷ in²)
Write 84 kg on the form. The 703 in the US formula is just the pound and inch conversions folded into one number, which is why both routes agree.
For medicine doses given per kilogram, convert carefully and let a pharmacist or doctor check the result. Mixing up lb and kg changes the dose by a factor of 2.2.
Luggage and Parcel Limits in Both Units
Airlines set bag limits in round kilograms and quote rounded pound figures, so the two don't match exactly. 23 kg is 50.7 lb, while 50 lb is only 22.68 kg. If you pack to 50 lb on a home scale you're within a 23 kg limit, but check your own airline's rules.
| Bag limit | kg | lb | Notes |
|---|---|---|---|
| Typical cabin bag allowance | 7 | 15.4 | Many European and Asian airlines |
| Larger cabin bag allowance | 10 | 22 | Common paid or premium carry-on |
| Standard checked bag | 23 | 50.7 | Sold as "50 lb" by US airlines |
| Heavy checked bag | 32 | 70.5 | Sold as "70 lb"; the most a single bag may weigh on many airlines |
| Parcel limit | lb | kg |
|---|---|---|
| USPS maximum (most services) | 70 | 31.75 |
| UPS and FedEx maximum per package | 150 | 68.04 |
Gym Plates: lb Sets vs kg Sets
US gyms mostly use pound plates and a 45 lb bar, while competition lifting uses kilogram plates and a 20 kg bar. They look alike but aren't interchangeable. A 45 lb plate is 20.41 kg, so two plates a side on a 45 lb bar is 225 lb (102.06 kg), while two 20 kg plates a side on a 20 kg bar is 100 kg (220.5 lb).
| lb plate | kg |
|---|---|
| 45 lb | 20.41 |
| 35 lb | 15.88 |
| 25 lb | 11.34 |
| 10 lb | 4.54 |
| 5 lb | 2.27 |
| 2.5 lb | 1.13 |
| kg plate | lb | Colour |
|---|---|---|
| 25 kg | 55.12 | Red |
| 20 kg | 44.09 | Blue |
| 15 kg | 33.07 | Yellow |
| 10 kg | 22.05 | Green |
| 5 kg | 11.02 | White |
A program written in kg, say 5 × 5 at 140 kg, works out to 308.6 lb, but with 2.5 lb as the smallest plate a lb gym loads in 5 lb steps: 305 or 310 lb. Round to the nearest load you can actually make.
Converting in Your Head
Three shortcuts, from rough to close:
- Halve it. 180 lb → 90 kg. Quick, but about 10% too high.
- Halve it, then take off a tenth. 180 → 90 → 90 − 9 = 81 kg. The real answer is 81.65 kg, so this is under 1% out, which is close enough for body weight or luggage.
- Multiply by 0.45. 180 × 0.45 = 81 kg. The same result, if you prefer one step.
Going the other way, double the kilograms and add a tenth of that: 70 kg → 140 + 14 = 154 lb (exact: 154.3 lb).
Where 0.45359237 Comes From
The pound has no physical standard of its own. Since 1959 it has been defined as exactly 0.45359237 kg, a figure agreed by the US, UK, Canada, Australia, New Zealand and South Africa so their pounds would finally match.
Before that, the US used the 1893 Mendenhall Order's value of 0.4535924277 kg, and the UK's pound differed very slightly. The difference is under a millionth of a kilogram per pound, so it only mattered in labs.
Because 0.45359237 is exact, multiplying by it gives the true answer. 2.20462 is a rounded reciprocal, so dividing by it, or multiplying kilograms by it, is very slightly off. This converter divides by 0.45359237 for kg → lb.
Frequently asked questions
How many kg is 1 lb?
0.45359237 kg, or about 454 grams. A pound is a little under half a kilogram.
Is 50 lb the same as 23 kg?
Not quite: 50 lb is 22.68 kg and 23 kg is 50.7 lb. Airlines use them as the same checked-bag limit, so a bag that weighs 50 lb on your scale is within a 23 kg allowance.
How do I write lb and kg correctly?
Use "lb" for pounds (from the Latin libra) and "kg" for kilograms, with a space before the unit: 150 lb, 68 kg. "lbs" is common but informal, and "kg" never takes an s.
Why does my scale show a slightly different kg figure?
Most bathroom scales round to 0.1 or 0.2 kg and 0.2 or 0.5 lb, and convert from a rounded reading. A difference of 0.1–0.2 kg between the lb and kg displays is normal.
Sources
- NIST Special Publication 811: pound (avoirdupois) = 0.45359237 kg exactly.
- Refinement of Values for the Yard and the Pound, 24 FR 5348 (1 July 1959): notice adopting the international yard and pound.
- USPS Domestic Mail Manual 101: 70 lb maximum weight for most mail.
- International Weightlifting Federation technical rules: 20 kg bar and colour-coded kg discs.
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