LBS to KG Converter
Convert pounds to kilograms (lb to kg) with the exact factor
1 pound = 0.45359237 kilograms exactly. To convert lbs to kg, multiply the pounds by 0.45359237, or divide them by 2.20462.
How to convert pounds to kilograms
This direction is the easy one, because the pound is defined in kilograms. Since 1959 the international avoirdupois pound has been exactly 0.45359237 kg, so multiplying by 0.45359237 gives an exact answer with no rounding at all. Dividing by 2.2 is a popular alternative, but 2.2 is itself a rounded number, so it adds a small error that the multiplication avoids. To go the other way, the kg to lbs converter uses the same definition, and the weight converter lists ounces, stone and tons too.
If your weight is in pounds and ounces, as with newborns and parcels, convert it to decimal pounds first by dividing the ounces by 16. 7 lb 8 oz becomes 7.5 lb, and 7.5 × 0.45359237 = 3.4019 kg. Adding the ounces as if they were a decimal (7.8 lb) is the most common error. For small kitchen amounts, the grams to ounces converter is a better fit.
Step by step
- Write the weight in decimal pounds (divide any ounces by 16 and add them).
- Multiply by 0.45359237.
- Round the kilograms: one decimal for body weight, three for parcels and freight.
- For grams, multiply the kilograms by 1,000.
See it on a scale
Worked examples
A 1 lb block of butter or pack of ground beef, a 150 lb adult, and a 7 lb 8 oz (7.5 lb) newborn baby.
1 lb × 0.45359237 = 0.45359237 kg
= 0.45359237 kg
150 lb × 0.45359237 = 68.038855 kg
= 68.038855 kg
7.5 lb × 0.45359237 = 3.4019428 kg
= 3.4019428 kg
Why is pound abbreviated lb?
Pound is abbreviated lb because the symbol comes from libra, the Roman unit of weight, whose name also meant a pair of balance scales. The word pound itself has a different Latin root, pondo, meaning “by weight”.
The same libra gives the pound sign £ used for British money, which began as the value of a pound weight of silver.
What about lbs? Style guides for units, including NIST SP 811, keep a unit symbol the same in the singular and the plural, so the correct forms are 1 lb and 150 lb. Lbs is an informal plural that everyone understands, and you will see it on luggage scales, gym equipment and the title of this page. The same rule covers the kilogram: write 68 kg, never 68 kgs.
The symbol never changes the arithmetic: 150 lb and 150 lbs are both 68.04 kg.
Is a pound a unit of mass or force?
Both exist: the pound (lb) on a scale is a unit of mass equal to 0.45359237 kg, while the pound-force (lbf) is the pull of standard gravity on that mass, exactly 4.4482216152605 N.
The pound-force is defined with standard gravity, 9.80665 m/s², so 1 lbf = 0.45359237 × 9.80665 N. Engineers use it for thrust, load ratings and pressure (psi means pounds-force per square inch), and the pounds to newtons converter handles those values.
For everyday weighing the distinction disappears. A bathroom scale senses the force on its platform and is calibrated to display mass, so converting a 150 lb reading to 68.04 kg is correct. The kilogram has the same split: the old kilogram-force (kgf) equals 9.80665 N and still appears on some gauges and tools, but it is not an SI unit.
Pounds to kg conversion chart
Pounds converted to kilograms, rounded to three decimal places. Every value is exact to that precision because the pound is defined as 0.45359237 kg.
| Pounds (lb) | Kilograms (kg) |
|---|---|
| 1 lb | 0.454 kg |
| 2 lb | 0.907 kg |
| 3 lb | 1.361 kg |
| 4 lb | 1.814 kg |
| 5 lb | 2.268 kg |
| 6 lb | 2.722 kg |
| 7 lb | 3.175 kg |
| 8 lb | 3.629 kg |
| 9 lb | 4.082 kg |
| 10 lb | 4.536 kg |
| 12 lb | 5.443 kg |
| 15 lb | 6.804 kg |
| 20 lb | 9.072 kg |
| 25 lb | 11.34 kg |
| 30 lb | 13.608 kg |
| 35 lb | 15.876 kg |
| 40 lb | 18.144 kg |
| 45 lb | 20.412 kg |
| 50 lb | 22.68 kg |
| 60 lb | 27.216 kg |
| 70 lb | 31.751 kg |
| 75 lb | 34.019 kg |
| 80 lb | 36.287 kg |
| 90 lb | 40.823 kg |
| 100 lb | 45.359 kg |
| 110 lb | 49.895 kg |
| 120 lb | 54.431 kg |
| 125 lb | 56.699 kg |
| 130 lb | 58.967 kg |
| 140 lb | 63.503 kg |
| 150 lb | 68.039 kg |
| 160 lb | 72.575 kg |
| 170 lb | 77.111 kg |
| 180 lb | 81.647 kg |
| 190 lb | 86.183 kg |
| 200 lb | 90.718 kg |
| 220 lb | 99.79 kg |
| 250 lb | 113.398 kg |
| 300 lb | 136.078 kg |
Pounds vs kilograms: which is bigger, and who uses each?
A pound is a little under half a kilogram. The two units measure the same thing, but they come from different traditions and turn up on different documents.
| Attribute | Pounds | Kilograms |
|---|---|---|
| Symbol | lb | kg |
| System | Imperial / US (avoirdupois) | Metric (SI base unit) |
| Defined as | 0.45359237 kg | 1 kg |
| One unit equals | 0.45359237 kg | 2.2046226 lb |
| What it measures | Mass; the pound-force (lbf) is a separate unit of force | Mass; the matching SI unit of force is the newton |
| Origin | The Roman libra, via the avoirdupois system of medieval English trade | The French metric system of the 1790s |
| Larger units | Stone (14 lb) and US short ton (2,000 lb) | Metric ton (1,000 kg) |
| Found on | US food packages, US airline and parcel limits, US gym plates | Medical records, prescriptions, international shipping forms, metric gym plates |
4 key differences
- One pound is 0.4536 kg, or about 453.6 g, a little less than half a kilogram.
- The pound converts to kilograms with a factor that ends after eight decimal places (0.45359237), so this direction never needs rounding until you choose to round the answer.
- A US short ton of 2,000 lb is 907.18 kg, about 9.3% less than a metric ton of 1,000 kg.
- Metric plates step through 1.25, 2.5, 5, 10, 15, 20 and 25 kg, while US plates step through 2.5, 5, 10, 25, 35 and 45 lb, so no US plate matches a metric plate exactly.
Pounds and ounces to kg: birth weights
US hospitals usually announce birth weight in pounds and ounces, while most of the world records it in kilograms or grams. This chart converts common birth weights exactly. For a baby's length, the inches to cm converter does the same job.
| Pounds and ounces | Decimal pounds | Kilograms | Grams |
|---|---|---|---|
| 5 lb 0 oz | 5 lb | 2.268 kg | 2,268 g |
| 5 lb 8 oz | 5.5 lb | 2.495 kg | 2,495 g |
| 6 lb 0 oz | 6 lb | 2.722 kg | 2,722 g |
| 6 lb 8 oz | 6.5 lb | 2.948 kg | 2,948 g |
| 7 lb 0 oz | 7 lb | 3.175 kg | 3,175 g |
| 7 lb 8 oz | 7.5 lb | 3.402 kg | 3,402 g |
| 8 lb 0 oz | 8 lb | 3.629 kg | 3,629 g |
| 8 lb 8 oz | 8.5 lb | 3.856 kg | 3,856 g |
| 9 lb 0 oz | 9 lb | 4.082 kg | 4,082 g |
| 9 lb 8 oz | 9.5 lb | 4.309 kg | 4,309 g |
| 10 lb 0 oz | 10 lb | 4.536 kg | 4,536 g |
Everyday pound limits in kilograms
Gym plates, baggage allowances and shipping limits in the US are set in round pounds. Here is what they mean in kilograms, which is what metric scales, foreign airlines and international forms ask for.
| Pounds | Kilograms | Where you see it |
|---|---|---|
| 2.5 lb | 1.13 kg | Smallest common US change plate |
| 5 lb | 2.27 kg | Small plate or light dumbbell |
| 10 lb | 4.54 kg | Plate or dumbbell |
| 25 lb | 11.34 kg | Plate |
| 35 lb | 15.88 kg | Plate; typical women's barbell in US gyms |
| 45 lb | 20.41 kg | Standard US barbell and large plate |
| 50 lb | 22.68 kg | Common US checked-bag limit |
| 51 lb | 23.13 kg | NIOSH lifting-equation load constant |
| 70 lb | 31.75 kg | USPS maximum parcel weight |
| 150 lb | 68.04 kg | UPS and FedEx Ground single-package maximum |
What is the quickest way to convert lbs to kg in your head?
The fastest mental method is halve it, then subtract 10%. That multiplies by 0.45, very close to the true 0.4536. For 180 lb: half is 90, 10% of 90 is 9, and 90 − 9 = 81 kg. The exact answer is 81.65 kg, so the shortcut is about 0.8% low.
If you have a phone calculator but not a converter, dividing by 2.2 is a little closer: 180 ÷ 2.2 = 81.82 kg, about 0.21% high. For anything where accuracy matters, multiply by 0.45359237 and there is nothing left to correct.
Two numbers worth remembering
- 100 lb ≈ 45.4 kg (exactly 45.35924 kg), so every 100 lb step adds about 45 kg.
- 10 lb ≈ 4.5 kg (exactly 4.535924 kg), handy for gym plates and grocery bags.
Body weight: pounds to kg and stone
Adult body weights from 100 to 300 lb, with the kilograms that medical records and most fitness apps outside the US use, and the stone and pounds familiar in the UK. Doctors in many countries record weight in kilograms because medication doses and BMI are calculated per kilogram.
| Pounds | Kilograms | Stone and pounds |
|---|---|---|
| 100 lb | 45.36 kg | 7 st 2 lb |
| 120 lb | 54.43 kg | 8 st 8 lb |
| 140 lb | 63.50 kg | 10 st 0 lb |
| 160 lb | 72.57 kg | 11 st 6 lb |
| 180 lb | 81.65 kg | 12 st 12 lb |
| 200 lb | 90.72 kg | 14 st 4 lb |
| 220 lb | 99.79 kg | 15 st 10 lb |
| 240 lb | 108.86 kg | 17 st 2 lb |
| 260 lb | 117.93 kg | 18 st 8 lb |
| 280 lb | 127.01 kg | 20 st 0 lb |
| 300 lb | 136.08 kg | 21 st 6 lb |
Why do doctors weigh patients in kilograms?
Doctors work in kilograms because many drug doses are prescribed in milligrams per kilogram of body weight, and body mass index is defined as kilograms divided by height in meters squared. That is why the feet to meters converter often goes hand in hand with this one. A slip between pounds and kilograms changes a result by a factor of 2.2, so for anything involving medication, always follow the dose your doctor or pharmacist gives you rather than converting it yourself.
A short history of the pound
England used several different pounds over the centuries, including the Tower pound and the troy pound of 12 troy ounces (about 373.24 g) that still survives for precious metals. The avoirdupois pound of 16 ounces became the everyday standard, but the US and UK definitions differed slightly until the 1959 agreement fixed it at 0.45359237 kg for both, and for Canada, Australia, New Zealand and South Africa. The UK wrote the same value into law with the Weights and Measures Act 1963.
Sources and further reading
The standards and references behind the numbers on this page. Links open in a new tab.
Standards and official sources
Pounds to kg FAQs
Short, exact answers to what people ask most.
How many kg is 1 lb?
One pound is exactly 0.45359237 kg, which is about 0.4536 kg or 453.6 grams. The value has been fixed by international agreement since 1959.
How do I convert pounds to kg without a calculator?
Halve the pounds, then subtract 10% of the result. For 200 lb, half is 100 and 100 − 10 = 90 kg; the exact answer is 90.72 kg.
What is 150 lbs in kg?
150 lb is 68.0389 kg, or about 68 kg. In the UK it would be written as 10 stone 10 pounds.
How do I convert pounds and ounces to kilograms?
Divide the ounces by 16 and add them to the pounds, then multiply by 0.45359237. For 8 lb 4 oz, that is 8.25 lb × 0.45359237 = 3.742 kg.
Is it better to divide by 2.2 or multiply by 0.4536?
Multiplying by 0.45359237 is exact. Dividing by 2.2 reads about 0.21% high, which is fine for body weight but not for freight, science or medication.
How many kg is a 45 lb plate?
A 45 lb plate is 20.41 kg, so it is slightly heavier than a 20 kg metric plate. A 45 lb bar loaded with two 45 lb plates is 135 lb, or 61.23 kg.
What is 200 lbs in kg?
200 lb is 90.718474 kg, about 90.7 kg. In the UK system it is 14 st 4 lb.
How many kg is 50 lbs?
50 lb is 22.679619 kg, about 22.7 kg, a little under the 23 kg bag limit many airlines use.
What is 120 lbs in kg?
120 lb is 54.431084 kg, or about 54.4 kg.
Related conversions
Pound defined as exactly 0.45359237 kg by the 1959 International Yard and Pound Agreement and the UK Weights and Measures Act 1963; pound-force, standard gravity and unit-symbol style from NIST SP 811; USPS and NIOSH published weight limits. Last updated . How we verify our numbers.