Last updated: November 7, 2026
To convert lbs to kg, multiply the number of pounds by 0.45359237, the exact factor fixed by international agreement in 1959. One pound equals about 0.454 kg, so 10 lb is 4.54 kg and 150 lb is 68.04 kg. For a fast estimate, divide pounds by 2.2.
Contents
- Lbs to kg formula
- How to convert lbs to kg step by step
- Lbs to kg conversion chart
- Body weight in pounds to kg
- How to convert lbs to kg in your head
- Pounds and ounces to kg
- Kg to lbs: converting the other way
- Why the pound is exactly 0.45359237 kg
- Frequently asked questions
Lbs to kg formula
The pounds to kg formula is a single multiplication:
kilograms = pounds × 0.45359237
The factor is exact. The 1959 notice from the U.S. National Bureau of Standards, now NIST, states that 1 pound (avoirdupois) equals 0.453 592 37 kilogram (Federal Register, 1959). NIST’s conversion tables list the same value rounded to 4.535 924 E-01 (NIST SP 811, Appendix B.9).
The abbreviation “lb” and the informal plural “lbs” mean the same unit, so the lbs to kg conversion factor and the lb to kg factor are identical.
How to convert lbs to kg step by step
- Write down the weight in pounds, for example 165 lb.
- Multiply it by 0.45359237: 165 × 0.45359237 = 74.84 kg.
- Round to a sensible precision. Two decimal places suits most uses; one decimal place is typical for body weight (74.8 kg).
- To check the answer, multiply the kilograms by 2.2. The result should land within about 0.2% of the original pounds.
If you only have a basic calculator, dividing by 2.2046 gives the same result to within a few grams for everyday weights.
Lbs to kg conversion chart
Values below use the exact factor and are rounded to two decimal places.
| Pounds (lb) | Kilograms (kg) |
|---|---|
| 1 lb | 0.45 kg |
| 2 lb | 0.91 kg |
| 5 lb | 2.27 kg |
| 10 lb | 4.54 kg |
| 20 lb | 9.07 kg |
| 25 lb | 11.34 kg |
| 50 lb | 22.68 kg |
| 100 lb | 45.36 kg |
| 150 lb | 68.04 kg |
| 200 lb | 90.72 kg |
| 250 lb | 113.40 kg |
| 300 lb | 136.08 kg |
For other everyday conversions, see the cooking conversion chart for cups, ounces and grams, and the guide to converting km to miles.
Body weight in pounds to kg
Many people search for this because a doctor’s office, a fitness app or a travel form asks for weight in kilograms. This lbs to kg weight chart covers 100 to 305 pounds, rounded to one decimal place.
| Pounds | Kilograms | Pounds | Kilograms |
|---|---|---|---|
| 100 lb | 45.4 kg | 105 lb | 47.6 kg |
| 110 lb | 49.9 kg | 115 lb | 52.2 kg |
| 120 lb | 54.4 kg | 125 lb | 56.7 kg |
| 130 lb | 59.0 kg | 135 lb | 61.2 kg |
| 140 lb | 63.5 kg | 145 lb | 65.8 kg |
| 150 lb | 68.0 kg | 155 lb | 70.3 kg |
| 160 lb | 72.6 kg | 165 lb | 74.8 kg |
| 170 lb | 77.1 kg | 175 lb | 79.4 kg |
| 180 lb | 81.6 kg | 185 lb | 83.9 kg |
| 190 lb | 86.2 kg | 195 lb | 88.5 kg |
| 200 lb | 90.7 kg | 205 lb | 93.0 kg |
| 210 lb | 95.3 kg | 215 lb | 97.5 kg |
| 220 lb | 99.8 kg | 225 lb | 102.1 kg |
| 230 lb | 104.3 kg | 235 lb | 106.6 kg |
| 240 lb | 108.9 kg | 245 lb | 111.1 kg |
| 250 lb | 113.4 kg | 255 lb | 115.7 kg |
| 260 lb | 117.9 kg | 265 lb | 120.2 kg |
| 270 lb | 122.5 kg | 275 lb | 124.7 kg |
| 280 lb | 127.0 kg | 285 lb | 129.3 kg |
| 290 lb | 131.5 kg | 295 lb | 133.8 kg |
| 300 lb | 136.1 kg | 305 lb | 138.3 kg |
Body mass index uses weight in kilograms, so this chart pairs well with our guide on how to calculate BMI.
How to convert lbs to kg in your head
To convert lbs to kg without a calculator, use the “halve it, then take off 10%” method:
- Divide the pounds by 2. For 180 lb, that is 90.
- Find 10% of that number: 9.
- Subtract: 90 − 9 = 81 kg.
The exact answer is 81.65 kg, so the shortcut runs slightly under, by about 0.8%. It works because halving and removing 10% is the same as multiplying by 0.45, close to the true 0.4536. NIST’s own quick-reference table uses 0.45 as the approximate pound-to-kilogram factor (NIST approximate conversions).
Pounds and ounces to kg
Baby weights, packages and recipes are often written in pounds and ounces. Because 1 pound is 16 ounces, convert in three steps:
- Divide the ounces by 16 to get a decimal pound. For 7 lb 8 oz, 8 ÷ 16 = 0.5, so the weight is 7.5 lb.
- Multiply by 0.45359237: 7.5 × 0.45359237 = 3.40 kg.
- For grams, multiply the kilograms by 1,000: about 3,402 g.
| Ounces (oz) | Grams (g) |
|---|---|
| 1 oz | 28.3 g |
| 4 oz | 113.4 g |
| 8 oz | 226.8 g |
| 12 oz | 340.2 g |
| 16 oz | 453.6 g |
NIST lists one avoirdupois ounce as 28.349 52 grams (NIST SP 811). Do not confuse it with the troy ounce used for gold and silver, which is about 31.10 grams.
Kg to lbs: converting the other way
To go from kilograms to pounds, divide by 0.45359237 or multiply by 2.20462. Airline baggage limits are often stated in kilograms, and 23 kg works out to about 50.7 lb.
| Kilograms (kg) | Pounds (lb) |
|---|---|
| 1 kg | 2.20 lb |
| 5 kg | 11.02 lb |
| 10 kg | 22.05 lb |
| 20 kg | 44.09 lb |
| 23 kg | 50.71 lb |
| 32 kg | 70.55 lb |
| 50 kg | 110.23 lb |
| 70 kg | 154.32 lb |
| 100 kg | 220.46 lb |
If you are packing for a flight, our TSA liquid rules guide covers what can go in a carry-on.
Why the pound is exactly 0.45359237 kg
Since 1893 the United States has defined the pound in terms of the kilogram rather than a physical pound standard. Small differences grew between countries, so effective July 1, 1959, the National Bureau of Standards adopted exact equivalents: 1 yard = 0.9144 meter and 1 pound = 0.45359237 kilogram. The same “international pound” was adopted by the national standards laboratories of Australia, Canada, New Zealand, South Africa and the United Kingdom (Federal Register, 1959).
The kilogram itself is now defined by fixing the numerical value of the Planck constant, so the pound is tied to a constant of nature as well (NIST, SI units: mass).
Mass vs weight
Strictly, pounds and kilograms in this guide measure mass. NIST notes that weight is the force gravity exerts on a body, but in everyday weights and measures “weight” is commonly used to mean mass, which is why a bathroom scale can read in either unit. The same idea applies to temperature scales in our Celsius to Fahrenheit guide: the conversion changes the number, not the thing being measured.
Frequently asked questions
How do you convert lbs to kg?
Multiply the number of pounds by 0.45359237. For example, 10 lb × 0.45359237 = 4.54 kg. For a quick estimate, divide pounds by 2.2.
Is 1 kg equal to 2.2 lbs?
Approximately. One kilogram equals about 2.20462 pounds, so 2.2 is a rounded figure that is close enough for everyday use but slightly low for precise work.
How many pounds is 1 kg?
One kilogram is about 2.20462 pounds. That number comes from dividing 1 by the exact pound definition of 0.45359237 kilogram.
What is the easiest way to convert lbs to kg?
Divide the pounds by 2, then subtract 10% of that result. For 150 lb, half is 75 and 10% of 75 is 7.5, giving 67.5 kg against an exact 68.04 kg.
Why is 1 pound exactly 0.45359237 kg?
In 1959 the United States and other English-speaking nations agreed on an international pound defined as exactly 0.45359237 kilogram. The U.S. National Bureau of Standards announced it in the Federal Register.
Sources
- National Bureau of Standards — Refinement of Values for the Yard and the Pound (Federal Register, 1959)
- NIST Special Publication 811, Appendix B.9: Conversion Factors
- NIST — Approximate Conversions from U.S. Customary Measures to Metric
- NIST — SI Units: Mass
Featured image: vintage beam scale by Pink Flojd, CC0, via Wikimedia Commons.