Convert lbs to kg instantly
Need a quick pounds-to-kilograms answer? Enter the weight in pounds below and the calculator will convert lbs to kg using the exact conversion factor of 1 lb = 0.45359237 kg.
For example, 100 lbs = 45.3592 kg, while 150 lbs = 68.0389 kg. Enter any pound value to get the result instantly.
The calculator uses the international avoirdupois pound, the standard pound used for everyday body weight, luggage, shipping and most product measurements.
How to convert lbs to kg
To convert lbs to kg, multiply the number of pounds by 0.45359237.
The formula is:
kilograms = pounds × 0.45359237
Or, written with unit symbols:
kg = lb × 0.45359237
The conversion factor is exact for the international avoirdupois pound. NIST lists the exact relationship as 1 lb = 0.45359237 kg.
Example: convert 150 lbs to kg
Suppose you need to convert 150 pounds to kilograms.
150 × 0.45359237 = 68.0388555 kg
Rounded to two decimal places:
150 lbs = 68.04 kg
For most everyday purposes, such as body weight or luggage, two decimal places are more than sufficient. The calculator above retains additional precision when it is useful.
Another example: 200 lbs to kg
Using the same formula:
200 × 0.45359237 = 90.718474 kg
Therefore:
200 lbs = 90.72 kg, rounded to two decimal places.
Why does 1 pound equal 0.45359237 kilograms?
The pound used for ordinary weight measurements is the international avoirdupois pound. Its relationship with the kilogram is fixed, so the conversion is not an estimate:
1 international avoirdupois pound = exactly 0.45359237 kilograms.
NIST distinguishes the ordinary avoirdupois pound from historical units such as the troy or apothecary pound, which have different values. For normal body weight, luggage, parcels and consumer goods, the avoirdupois pound is the relevant unit.
This distinction is useful because simply saying “pound” without understanding the measurement system can occasionally lead to conversion errors in historical or specialist contexts.
What are pounds and kilograms?
A pound, with the standard unit symbol lb, is a unit of mass commonly used for everyday measurements in systems that use customary or imperial units. You may also see the informal plural abbreviation lbs, which is why searches such as “convert lbs to kg” are common.
A kilogram, symbol kg, is the SI base unit of mass and is part of the International System of Units.
Since 20 May 2019, the kilogram has no longer been defined by the mass of a physical prototype. It is defined through the fixed numerical value of the Planck constant, h, which is exactly 6.62607015 × 10⁻³⁴ J s.
In everyday conversation, people often use the word “weight” when talking about pounds and kilograms. Technically, however, pounds and kilograms in this context are units used to express mass.
Pounds vs Kilograms: What’s the Difference?
Pounds (lb) and kilograms (kg) both measure mass, but they belong to different measurement systems and represent different amounts.
The kilogram is the SI base unit of mass and is used throughout most of the world. The pound is commonly used for body weight and other everyday measurements in the United States and in some contexts in the United Kingdom.
The exact relationship between the two units is:
1 lb = exactly 0.45359237 kg
In the opposite direction:
1 kg ≈ 2.20462 lb
This means that a kilogram is more than twice as large as a pound.
For example:
- 10 lbs = 4.54 kg
- 50 lbs = 22.68 kg
- 100 lbs = 45.36 kg
- 1 kg = 2.20 lbs
- 10 kg = 22.05 lbs
- 50 kg = 110.23 lbs
lbs vs kg at a glance
| Feature | Pounds (lb) | Kilograms (kg) |
|---|---|---|
| Unit symbol | lb | kg |
| Measurement | Mass | Mass |
| Measurement system | US customary / avoirdupois | International System of Units (SI) |
| Relative size | Smaller unit | Larger unit |
| Conversion | 1 lb = 0.45359237 kg | 1 kg ≈ 2.20462 lb |
| Common use | Body weight, products, luggage and shipping in the US | Body mass, products, luggage, science and commerce internationally |
Which is heavier: 1 lb or 1 kg?
One kilogram is heavier than one pound.
A kilogram is approximately 2.20462 pounds, while one pound is only 0.45359237 kilograms.
For example, a person weighing 100 kg weighs approximately 220.46 lbs, whereas a person weighing 100 lbs weighs approximately 45.36 kg.
Why do some countries use pounds while others use kilograms?
Kilograms are part of the International System of Units (SI) and are the standard unit of mass in most countries.
Pounds remain widely used in the United States for everyday measurements such as body weight, packaged goods and luggage. This is why lbs to kg conversion is particularly useful when comparing measurements between US customary and metric systems.
If you already have a value in pounds, use the lbs to kg calculator above for an accurate conversion rather than relying on a rough estimate.
When do you need to convert lbs to kg?
People need pounds-to-kilograms conversions whenever information expressed in pounds must be compared with, entered into or understood in a metric context.
Body weight and fitness
A bathroom scale, fitness tracker, training plan or international form may use a different unit from the one you normally use. If your scale displays pounds but an app requests kilograms, an accurate conversion lets you transfer the measurement without guessing.
For example:
180 lbs × 0.45359237 = 81.6466 kg
So 180 lbs is approximately 81.65 kg.
If the converted value will be used in another calculation, keep more decimal places until the final step instead of repeatedly rounding intermediate values.
Travel and luggage
Travel is another common situation where pounds and kilograms meet. A traveler may own a luggage scale marked in pounds while an airline or booking document presents a baggage allowance in kilograms.
Converting the measurement before leaving home makes it easier to compare the two values and reduces the risk of relying on an inaccurate mental estimate.
Shipping and parcels
Package weights may be supplied in pounds by one company and required in kilograms by another system.
Accurate conversion matters more as the package becomes heavier. Using 0.45 kg per pound rather than the exact factor may look harmless for a small parcel, but the rounding difference grows with larger values.
Product specifications and equipment
Weights for exercise equipment, tools, outdoor gear, appliances and other products may be published in pounds in one market and kilograms in another.
Converting the figures allows users to compare products using the same measurement system instead of trying to interpret two different unit conventions.
International and technical data
The kilogram is part of the SI, the internationally used measurement system. Converting pound measurements to kilograms is therefore useful when customary-unit data needs to be compared with specifications, datasets or documentation expressed in SI units.
Exact conversion vs. quick mental calculation
For an accurate result, use:
lbs × 0.45359237
For a quick mental estimate, you may sometimes see the shortcut:
lbs ÷ 2.2
For example:
100 ÷ 2.2 ≈ 45.45 kg
The exact conversion is:
100 × 0.45359237 = 45.359237 kg
The shortcut is useful for rough estimation, but it should not replace the exact factor when accuracy matters.
Another rough shortcut is to treat 1 lb as 0.45 kg. Again, this is convenient for mental arithmetic but is not the defined conversion value.
How accurate is the lbs to kg conversion?
The underlying conversion itself is exact:
1 lb = 0.45359237 kg
Any difference between displayed results therefore comes from rounding, not uncertainty in the conversion factor.
For example:
75 lbs = 34.01942775 kg
This could reasonably be displayed as:
34.0194 kg for higher precision, or
34.02 kg for normal everyday use.
Our calculator performs the calculation using the full conversion factor before displaying the result.
Common mistakes when converting pounds to kilograms
One of the most common errors is using 0.45 as though it were the exact conversion factor. It is only an approximation.
Another mistake is rounding too early. If a converted number will be used in another calculation, perform the conversion first and round the final result afterward.
It is also important not to confuse the pound as a unit of mass with pound-force (lbf), which is a unit of force. This calculator converts ordinary avoirdupois pounds to kilograms and is intended for mass measurements such as body mass, luggage, parcels and product weights.
Finally, remember that lb is the internationally recognized unit symbol for pound. “Lbs” is widely used informally for plural pounds, but the symbol itself does not change between singular and plural.
Pounds to kilograms conversion examples
Here are several common conversions using the exact factor:
| Pounds | Kilograms |
|---|---|
| 5 lbs | 2.26796 kg |
| 25 lbs | 11.33981 kg |
| 50 lbs | 22.67962 kg |
| 75 lbs | 34.01943 kg |
| 100 lbs | 45.35924 kg |
| 125 lbs | 56.69905 kg |
| 150 lbs | 68.03886 kg |
| 175 lbs | 79.37866 kg |
| 200 lbs | 90.71847 kg |
Related weight converters
If you regularly switch between metric and customary units, you may also find these Easy Unit Convert tools useful:
Kilograms to Pounds – for converting kg back to lb.
Kilograms to Stones – useful for kilogram and stone measurements.
Pounds to Stones – for converting pounds into stones and pounds.
Ounces to Grams – for smaller weight and mass measurements.
Weight Converters – browse all available weight conversion tools.
Convert lbs to kg chart: 1 to 100 pounds
The table below provides quick reference values for common pound measurements. Results are calculated using the exact factor 1 lb = 0.45359237 kg and rounded to four decimal places.
| Pounds (lb) | Kilograms (kg) |
|---|---|
| 1 lb | 0.4536 kg |
| 10 lbs | 4.5359 kg |
| 20 lbs | 9.0718 kg |
| 30 lbs | 13.6078 kg |
| 40 lbs | 18.1437 kg |
| 50 lbs | 22.6796 kg |
| 60 lbs | 27.2155 kg |
| 70 lbs | 31.7515 kg |
| 80 lbs | 36.2874 kg |
| 90 lbs | 40.8233 kg |
| 100 lbs | 45.3592 kg |
Frequently asked questions
Multiply the number of pounds by 0.45359237. For example, 100 lbs × 0.45359237 = 45.359237 kg, so 100 lbs is approximately 45.36 kg.
Yes. For the international avoirdupois pound used for ordinary measurements, 1 lb is exactly 0.45359237 kg.
100 lbs = 45.359237 kg, or approximately 45.36 kg when rounded to two decimal places.
150 lbs = 68.0388555 kg, which is approximately 68.04 kg.
200 lbs = 90.718474 kg, which rounds to 90.72 kg.
Yes, dividing by 2.2 gives a useful rough estimate, but it is not as accurate as multiplying by 0.45359237. Use the exact conversion factor when precision is important.
They refer to the same unit. lb is the standard symbol for pound and remains unchanged in the plural. lbs is a common informal abbreviation for multiple pounds and is frequently used in everyday searches and writing.
The kilogram is the SI base unit of mass. The International System of Units provides a standardized measurement framework used internationally for science, engineering, commerce and many other applications.
No. This calculator converts avoirdupois pounds as a unit of mass to kilograms. Pound-force (lbf) is a unit of force and is a different physical quantity.
Sources and measurement references
The conversion values used on this page are based on recognized international measurement standards.
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement: lists 1 avoirdupois pound as exactly 0.45359237 kilograms.
- BIPM – The International System of Units (SI): defines the kilogram as the SI base unit of mass through the fixed numerical value of the Planck constant.
For more information, see the official measurement standards published by the National Institute of Standards and Technology (NIST) and the International Bureau of Weights and Measures (BIPM).
