Pounds (lb) to Kilograms (kg) Conversion
Pounds
The pound (avoirdupois) is a unit of mass equal to exactly 0.45359237 kilograms, standardised in 1959. It is the primary unit of mass in the US customary and British imperial systems, used for body weight, food packaging, and commercial transactions. The pound is subdivided into 16 ounces. In US engineering, the distinction between pound-mass (lbm) and pound-force (lbf) is a frequent source of calculation errors.
Kilograms
The kilogram is the SI base unit of mass. From 1889 to 2019, it was defined by the International Prototype of the Kilogram — a physical cylinder of platinum-iridium alloy stored near Paris. In 2019, the kilogram was redefined in terms of Planck's constant (h = 6.62607015 × 10⁻³⁴ J·s), making it the first base unit defined entirely by a fundamental constant of nature. This eliminated the risk of the kilogram gradually changing mass due to contamination of the physical prototype.
| Pounds (lb) | Kilograms (kg) |
|---|---|
| 0.1 lb | 0.0454 kg |
| 1 lb | 0.4536 kg |
| 2 lb | 0.9072 kg |
| 3 lb | 1.3608 kg |
| 5 lb | 2.268 kg |
| 10 lb | 4.5359 kg |
| 20 lb | 9.0718 kg |
| 30 lb | 13.6078 kg |
| 50 lb | 22.6796 kg |
| 100 lb | 45.3592 kg |
| 1000 lb | 453.5924 kg |
Frequently Asked Questions (FAQ)
How many kilograms are in 1 pounds?
1 pounds (lb) is exactly 0.453592 kilograms (kg).
How do I convert pounds to kilograms?
Multiply the value in pounds by 0.453592 to get the result in kilograms. Or use the converter above — type any number and see the result instantly.
How do I convert pounds to kilograms?
Multiply pounds by 0.453592 to get kilograms. The exact definition is 1 lb = 0.45359237 kg. Quick references: 100 lb = 45.36 kg, 150 lb = 68.04 kg, 175 lb = 79.38 kg, 200 lb = 90.72 kg. Reliable mental shortcut: halve the pound value and subtract 10% — for 160 lb: 160/2 = 80, minus 8 = 72 kg (exact: 72.57 kg). This works within 1% for any everyday body weight.
What is the difference between pounds (lb), troy pounds, and stones?
The common pound (avoirdupois) used for everyday weight is 453.592 g with 16 ounces. The troy pound, used exclusively for precious metals like gold and silver, is 373.242 g with 12 troy ounces — about 18% lighter. The stone is a UK unit equal to exactly 14 avoirdupois pounds (6.350 kg), still widely used for human body weight in the UK and Ireland. "11 stone 4" means 11 × 14 + 4 = 158 lb = 71.67 kg. Understanding these distinctions matters when reading older texts or UK health records.