The short answer
1 kilogram = 2.20462262185 pounds. Multiply kilograms by 2.20462 to get pounds.
pounds = kilograms × 2.2046226218
kilograms = pounds × 0.4535923770 kg × 2.20462 = 154.32 lb.
The definition behind it
The international avoirdupois pound is defined as exactly 0.45359237 kilograms (1959 International Yard and Pound Agreement). The kilogram, since the 2019 SI redefinition, is fixed by the Planck constant rather than a metal cylinder in Sèvres — so the conversion is exact by definition and stable forever.
Body-weight chart
| Kilograms | Pounds | Stone + pounds (UK) |
|---|---|---|
| 50 kg | 110.2 lb | 7 st 12 lb |
| 60 kg | 132.3 lb | 9 st 6 lb |
| 70 kg | 154.3 lb | 11 st 0 lb |
| 80 kg | 176.4 lb | 12 st 8 lb |
| 90 kg | 198.4 lb | 14 st 2 lb |
| 100 kg | 220.5 lb | 15 st 10 lb |
One stone = 14 lb = 6.35029318 kg, still standard for body weight in the UK and Ireland.
Mental shortcuts
- Double it and add 10%. 65 kg → 130 + 13 = 143 lb (true 143.3). Accurate to ~0.2%.
- Halve pounds and subtract 10% for the reverse: 180 lb → 90 − 9 = 81 kg (true 81.6).
Mass vs weight
Kilograms and pounds as used day to day both measure mass. Physics separates them: the pound-force (lbf) and newton (N) measure force. On Earth, 1 kg exerts 9.80665 N — the standard gravity value set by the CGPM. Confusing pound-mass with pound-force is the classic engineering slip; in the slug/lbf system, 1 slug = 32.174 lb-mass.
Pounds that are not the pound
| Unit | In kilograms | Used for |
|---|---|---|
| Avoirdupois pound | 0.45359237 kg | Everyday weight |
| Troy pound | 0.3732417216 kg | Precious metals |
| Metric pound (Pfund) | 0.5 kg | Informal, Germany/Netherlands |
| Ounce (avoirdupois) | 0.028349523 kg | 1/16 lb |
| Troy ounce | 0.0311034768 kg | Gold, silver bullion |
Gold quoted "per ounce" is always a troy ounce — 10% heavier than the kitchen ounce. Mixing them misprices bullion by roughly 9.7%.
Where precision matters
- Medication dosing is calculated in mg/kg. Converting a patient's pounds to kilograms with 2.2 instead of 2.20462 introduces a 0.2% error — negligible for adults, but paediatric and chemotherapy protocols require the full factor.
- Airline baggage: a 23 kg allowance is 50.7 lb, so a 50 lb bag passes; a 20 kg limit is only 44.1 lb.
- Shipping tariffs round up per kilogram, so convert then round, never the reverse.
Key takeaways
- 1 lb = 0.45359237 kg exactly; 1 kg = 2.20462262 lb
- "Double and add 10%" is accurate enough for daily use
- Troy ounces and pounds are a different system — never mix with avoirdupois
- Keep full precision for medical and legal weights