How this works
1 kg ≈ 2.20462 lb (the reciprocal of the exact 1 lb = 0.45359237 kg defined in the 1959 international yard-and-pound agreement). Useful for body weight when crossing imperial/metric boundaries, gym plate calculations, shipping weights, and any cooking recipe written in pounds.
The "pound" you need almost certainly means the international avoirdupois pound (the standard one — used for body weight, groceries, parcels, and pretty much all everyday measurement in the US and UK). But the word is overloaded. The troy pound (373.24 g) survives in precious metals — gold and silver are still quoted in troy ounces (1 troy oz = 31.10 g, 12 troy oz = 1 troy lb). The German *Pfund* and French *livre* both colloquially mean exactly 500 g — half a kilogram — and you'll see them on butcher counters and in older recipes despite not being legal trade units. If a recipe calls for "1 Pfund Mehl" it means 500 g, not 453.6 g.
For mental conversion, the cleanest shortcut is "double and add 10%": kg × 2 then add a tenth of the original. So 70 kg → 140 + 7 = 147... not quite right. Better: kg × 2.2 — within 0.2% — so 70 kg ≈ 154 lb (actual 154.32). For going the other way (lb to kg), halve and subtract 10%: 150 lb → 75 − 7.5 = 67.5 kg (actual 68.04). These shortcuts are close enough for body weight, recipes, and luggage; use the calculator when accuracy matters (medication dosing, shipping fees that round on the kg).
The formula
For mental conversion, multiply kg by 2.2 — gives ~0.2% error. So 70 kg ≈ 154 lb (actual 154.32), 80 kg ≈ 176 lb (actual 176.37). The ÷ 0.45359237 form looks intimidating but is exact; the × 2.20462 form is one rounding step removed but easier to remember.
Example calculation
- 1 kg = 2.205 lb
- 5 kg = 11.02 lb
- 70 kg = 154.32 lb (≈ adult weight)
- 23 kg = 50.71 lb (typical airline checked-bag limit)
Frequently asked questions
Why is the conversion 2.20462 and not a round number?
Because the kilogram and the pound were defined independently — the kg from a fraction of the Earth's circumference (later from a platinum-iridium prototype, now from physical constants), the pound from medieval English commerce. They were only formally pinned together in 1959 with 1 lb = 0.45359237 kg. The 2.20462 is just 1 / 0.45359237.
How heavy is the typical airline carry-on / checked bag in lb?
Typical carry-on limits are 7-10 kg = 15.4-22 lb. Checked-bag limits run 20-23 kg = 44.1-50.7 lb in economy, 30-32 kg = 66.1-70.5 lb in business/first. The US 50-lb domestic checked-bag limit comes out to 22.68 kg, which is why 23 kg is so common as the international rounded equivalent.
What's the easiest way to convert kg to lb in my head?
Multiply kg by 2.2 — that's within 0.2% of the exact factor (2.20462), which is well below grocery-scale precision. So 50 kg → 110 lb (exact 110.23), 80 kg → 176 lb (exact 176.37), 100 kg → 220 lb (exact 220.46). For more precision in the head, use "× 2 + 10%": 70 kg → 140 + 14 = 154 lb (exact 154.32). Going from lb to kg is just the reverse — divide by 2 then subtract 10% — so 200 lb → 100 − 10 = 90 kg (exact 90.72).
What's a stone in kg, and why do British people use them?
1 stone = 14 lb = 6.35029 kg exactly. Stones are used almost exclusively for body weight in the UK and Ireland — gym scales, doctor's offices, and casual conversation all default to "11 stone 4" instead of "158 lb" or "71.7 kg". The reason is historical inertia: stones were a standard British market unit until decimalisation, and the format (whole stones plus residual pounds) maps neatly onto the typical adult range of 8–20 stone. To convert: take stones × 6.35 for kg, or stones × 14 for pounds. So 12 stone = 76.2 kg = 168 lb.
Does a kg weigh exactly 2.20462 lb everywhere on Earth?
Yes for mass — which is what kg and lb actually measure. The conversion 1 kg = 2.20462 lb is a definition, fixed and global. What changes with location is *weight* — the force of gravity acting on that mass. Gravity is about 0.5% weaker at the equator than at the poles (Earth bulges, so you're further from the centre) and weakens further with altitude. A kitchen or bathroom scale calibrated at the factory in one country will read very slightly differently in another, but the error is well below the scale's display precision unless you take it from sea level to a mountain summit. For luggage, body weight, and groceries, treat the conversion as exact.