Pounds to Kg Converter
Convert pounds to kilograms and kg to lbs instantly — type in either field. 1 lb = 0.4536 kg.
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Pounds ↔ Kilograms
The exact definition: 1 pound = 0.45359237 kilograms, so 1 kg ≈ 2.2046 lb. Quick mental math: halve the pounds and take a bit less (150 lb → ~68 kg); or double the kilograms and add 10% (70 kg → 154 lb). Type in either box — the other converts live, along with a stones value for readers used to the UK body-weight system.
Because the pound-to-kilogram ratio is fixed to eight decimal places by international definition, there's no rounding ambiguity to worry about: a package labeled 5 lb in the US and one labeled 2.27 kg in Europe describe the exact same physical weight, not an approximation of it. That precision matters most in fields like pharmaceuticals, shipping and sports, where a mislabeled decimal point has real consequences. This kind of exactness is a fairly modern convenience — for most of history "a pound" varied by region and even by the commodity being weighed, which made cross-border trade genuinely error-prone until international standardization caught up with global commerce.
Good to Know
The word "pound" traces back to the Latin libra pondo ("a pound by weight") — which is exactly why the abbreviation is "lb" and not "pd", a small etymological mismatch that trips up a lot of people. The 0.45359237 kg figure is the avoirdupois pound, the everyday one used for body weight, groceries and general goods, and it was fixed by the same 1959 international agreement that standardized the foot and inch across the US, UK, Canada, Australia, New Zealand and South Africa. "Avoirdupois" itself comes from the Old French avoir de pois, meaning "goods of weight" — the trade system historically used for anything sold by weight rather than by count or volume. It's easy to confuse with the far rarer troy pound (about 373 grams), a separate historical unit used almost exclusively for weighing precious metals and gemstones — a "pound" of gold and a "pound" of apples are not the same number of grams, and troy weight even divides into 12 ounces per pound instead of 16.
- UFC lightweight limit: 155 lb = 70.3 kg
- UFC heavyweight limit: 265 lb = 120.2 kg
- Typical airline checked-bag limit: 50 lb = 22.7 kg
- Average newborn weight: about 7.5 lb = 3.4 kg
- Common gym plate: 45 lb = 20.4 kg
Frequently Asked Questions
How many kg is 180 pounds?
180 lb = 81.65 kg (180 × 0.45359237). Common body weights: 150 lb = 68.0 kg, 200 lb = 90.7 kg, 220 lb = 99.8 kg. Because the conversion factor is an internationally fixed constant rather than a rounded approximation, these figures match any properly built calculator to the same decimal place.
How many pounds is 70 kg?
70 kg = 154.3 lb (70 × 2.20462). The quick mental estimate — double the kilograms and add 10% — gives 154, right on target for everyday use. For anything precision-sensitive, like a shipping label or a medication dose, it's worth using the exact multiplier instead of the shortcut.
What's the difference between a troy pound and a regular pound?
The pound used for body weight and everyday goods is the avoirdupois pound (0.45359237 kg) — what this converter uses. The troy pound (about 373 g) is a separate, older unit used almost exclusively for weighing gold, silver and gemstones, and it divides differently too: 12 troy ounces per troy pound instead of 16. A jeweler quoting "price per pound" of silver is not using the same pound as a bathroom scale.
Why is "pound" abbreviated as "lb"?
It comes from the Latin libra pondo, meaning "a pound by weight." The abbreviation lb comes from libra — the noun for the unit itself — even though the English word "pound" descends from pondo, the second half of the phrase. The same Latin root also explains why the UK currency symbol for pounds sterling is £.
What do lb and kg look like in combat sports weight classes?
In the UFC, lightweight fighters weigh in at 155 lb (70.3 kg), welterweight at 170 lb (77.1 kg), and heavyweight up to 265 lb (120.2 kg). Featherweight, at 145 lb (65.8 kg), and bantamweight, at 135 lb (61.2 kg), round out the lighter divisions. US boxing and MMA commissions set official limits in pounds, but international broadcasts and record books usually list the kilogram equivalent alongside it for audiences outside the US.
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