Pounds to Kilograms
Convert pounds to kilograms instantly. Free, fast, no signup.
How to use this tool
- Enter pounds in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your kilograms and the full breakdown beneath it.
Convert pounds to kilograms instantly. Free, fast, no signup.
Formula
Kilograms = Pounds × 0.45359237
One avoirdupois pound is defined as exactly 0.45359237 kilograms.
How it works
Multiply the number of pounds by 0.45359237 to obtain kilograms. This is an exact defined relationship established in 1959 — no rounding is inherent in the factor itself. The result for whole-number pound inputs will generally be a non-terminating decimal, so answers are typically rounded to four decimal places for display.
Common mistake: A common shortcut is to divide by 2 (or 2.2), which significantly overestimates the kilogram equivalent. Dividing by 2 gives 0.5 kg for 1 lb, versus the correct 0.4536 kg — an error of more than 10%.
Worked example
Convert 1 pound to kilograms
- Start with 1 pound.
- Multiply by the exact definition: 1 × 0.45359237.
- Round to four decimal places: 0.4536 kg.
1 pound = 0.4536 kilograms
Common mistakes to avoid
- Using 0.45 instead of the exact 0.45359237, overstating the kilogram result by about 0.8% -- meaningful when tracking body weight across weeks.
- Confusing avoirdupois pounds (lbs) with troy pounds used in precious metals -- 1 troy pound = 0.3732 kg, not 0.4536 kg.
- Multiplying by 2.2046 instead of dividing (or multiplying by 0.4536) -- that converts kilograms to pounds.
Key terms
- Pound (lb)
- A unit of mass in the avoirdupois system equal to exactly 0.45359237 kg, used daily in the United States.
- Kilogram (kg)
- The SI base unit of mass; all other mass units in the metric system are derived from it.
- Avoirdupois system
- The everyday weight system used in the US and UK, where 1 lb = 16 oz and 14 lb = 1 stone.
- Defined constant
- A value fixed by international agreement, such as 1 lb = 0.45359237 kg, that carries no measurement uncertainty.
Frequently asked questions
- How do I convert pounds to kilograms?
- Multiply the number of pounds by 0.453592 to get kilograms.