Authoritative definitions of the International System of Units and SI prefixes.
Dedicated unit pair
Pounds to Kilograms
Convert lb to kg instantly, then review the formula, assumptions, and rounding guidance.
Weight & massInstant result
Decimals
Formula result = input × 0.45359237 ÷ 1. 1 lb = 0.4536 kg
Common examples
One value, several units
Kilograms0.4536 kg
Grams453.5924 g
Milligrams453,592.37 mg
Metric tonnes0.0005 t
Ounces16 oz
Stone0.0714 st
Conversion table
| lb | kg |
|---|---|
| 1 lb | 0.4536 kg |
| 2 lb | 0.9072 kg |
| 5 lb | 2.268 kg |
| 10 lb | 4.5359 kg |
| 25 lb | 11.3398 kg |
| 50 lb | 22.6796 kg |
| 100 lb | 45.3592 kg |
Conversion chart
1 lb0.4536 kg
5 lb2.268 kg
10 lb4.5359 kg
25 lb11.3398 kg
50 lb22.6796 kg
Worked example
1 kilogram equals 2.20462 pounds.
Unit definition
Pounds (lb) One pounds equals 0.45359237 kilogram.
Unit history
Pounds is represented here using its modern SI definition or an internationally accepted relationship to an SI base unit.
Step by step
1. Parse the value, including fractions.
2. Convert lb to kilogram.
3. Convert the base value to kg and apply your display precision.
Understand the result before using it
Pounds to Kilograms converts a value measured in Pounds (lb) into the equivalent value in Kilograms (kg). The numerical value changes because the size and definition of the selected unit changes; the underlying quantity does not.
Calculated result
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.
Formula, assumptions, and example
Formula
result = input × 0.45359237 ÷ 1
Assumptions
- Pounds and Kilograms represent the same weight & mass quantity.
- The input is expressed in lb; the output is expressed in kg.
- The unit definitions and conventional relationship shown on this page apply.
Worked example
1 lb = 0.45359237 kg. For another value, apply the same relationship and round only to the precision your source measurement supports.
When to use it
Good uses
- Read a lb measurement in a document that expects kg.
- Compare a pounds value with a value reported in kilograms.
- Check the lb-to-kg arithmetic before copying the result into another calculation.
Limitations
Common mistakes to avoid
- Everyday language often says weight, but these units represent mass. Force requires a local gravitational acceleration.
- Round the output to a precision justified by the original measurement.
- Verify safety-critical, regulated, laboratory, and contractual conversions against the controlling standard.
Sources and further reading
These references explain the underlying standards or provide authoritative context. Your own contract, institution, clinician, product documentation, local code, or governing standard may be the controlling source.
Guidance on unit names, symbols, conversions, and numerical presentation.
Questions about this calculation
How do I convert Pounds to Kilograms?
result = input × 0.45359237 ÷ 1 Using the displayed relationship, 1 lb equals 0.45359237 kg.
How many Kilograms are in one Pounds?
One Pounds is 0.45359237 Kilograms. The displayed digits may be rounded.
Can I reverse the lb to kg conversion?
Yes. Swap the source and target units in the converter. The reverse relationship converts kg back to lb.
Is the Pounds to Kilograms result exact?
The conversion follows the displayed unit relationship. Display rounding can hide additional digits, and measured inputs cannot become more accurate merely by changing units.