Pounds to Kilograms
Convert any value from pound to kilogram with full precision. Use the converter above for instant results, or read on for the exact formula, worked examples, common uses, and answers to frequently asked questions.
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About the Pound to Kilogram conversion
Mass and weight conversions come up everywhere — in cooking, shipping, science, fitness, and international trade. Although mass and weight are technically different (mass is the amount of matter, weight is the force gravity exerts on that matter), the everyday conversions between pounds, kilograms, ounces, grams, and stones are what most people need.
This page focuses specifically on converting pound to kilogram. Use the converter above for instant results, or read on for what each unit is, the exact formula, a worked example, and answers to common questions.
Understanding pound and kilogram
What is a pound?
The pound is defined as exactly 0.45359237 kilogram under the 1959 international agreement, and it divides into 16 ounces. It is the everyday unit of body weight and general mass in the United States.
What is a kilogram?
The kilogram is the SI base unit of mass. Since 2019 it has been defined by fixing the value of the Planck constant, replacing the old platinum-iridium cylinder kept near Paris. It is the reference for all metric mass units and the standard unit of mass worldwide in science and commerce.
How a pound compares to a kilogram
The kilogram is the larger of the two units: it takes about 2.20462262 pound to make a single kilogram. Because the pound is smaller, the same length or quantity works out to a larger number when you measure it with that unit. Knowing which unit is larger is a quick way to sanity-check a conversion: if the numbers move in the wrong direction, the two units have probably been swapped.
Conversion formula
The exact mathematical relationship between pound and kilogram is:
1 pound = 0.45359237 kilogram
So to convert a value V from pound to kilogram, use:
Vkilogram = Vpound × 0.45359237
To go in the opposite direction:
Vpound = Vkilogram × 2.20462262
These factors come from the international definitions published by NIST, BIPM, and ISO 80000 and are exact within their respective standard systems. The converter applies them with full floating-point precision.
Worked example
Using the formula above, here are some common values converted from Pound to Kilogram:
| Pound | Kilogram |
|---|---|
| 1 | 0.453592 |
| 5 | 2.267962 |
| 10 | 4.535924 |
| 25 | 11.339809 |
| 50 | 22.679619 |
| 100 | 45.359237 |
Sources and accuracy
The kilogram was redefined in 2019 by fixing the Planck constant (NIST, BIPM). All metric mass units derive from this base. The international avoirdupois pound (0.45359237 kg) was agreed in the 1959 international yard and pound agreement between English-speaking nations. Troy weights (used for precious metals) follow the troy system standardized in 1828 by the U.S. Mint.
Conversion factors are cross-checked against the NIST SP 811 guide, the BIPM SI brochure, and ISO 80000, plus published historical references for older unit systems. For mission-critical work such as medical dosing, legal-for-trade measurement, aerospace, or large-scale engineering, always verify independently with the original source.
Practical tips
A common source of error is mixing troy and avoirdupois ounces: one troy ounce is about 31.1 g while one avoirdupois ounce is about 28.35 g. Use the troy ounce option only when measuring gold, silver, platinum, or gemstones.
Frequently asked questions
How many kilogram are in one pound?
One pound equals 0.45359237 kilogram. To convert, multiply your pound value by 0.45359237.
Which is bigger, a pound or a kilogram?
The kilogram is bigger. One pound is only about 0.45359237 kilogram.
How accurate is this pound to kilogram converter?
It uses the official international conversion factors from NIST and BIPM with full double-precision floating-point accuracy. For everyday use the result is precise to many more decimal places than any practical measurement requires.
Can I convert kilogram back to pound as well?
Yes. Use the swap button above to reverse the From and To fields, or change either dropdown to any unit in the weight & mass category. The calculation runs entirely in your browser, so it also works offline once the page has loaded.