Convert mass from the international avoirdupois pound (lb) to the SI base unit kilogram (kg). This calculator applies the exact legal definition 1 lb = 0.45359237 kg.
Convert Pounds to Kilograms (lb → kg)
Enter pounds and press Convert
Pounds (lb)
Result in Kilograms (kg)
How to use
- Enter a value in pounds in the input field.
- (Optional) Set Decimal Places to control rounding.
- Click Convert to get kilograms; the calculation line shows the factor used.
- Use Copy Result to place the output on your clipboard.
- Click Clear All to reset every field.
- Swap takes you to the inverse calculator (kg → lb).
Definitions of measurement units
Pound (lb, avoirdupois) — Unit of mass in the US customary and British imperial systems, defined exactly as 0.45359237 kilogram. Relations used here: 1 lb = 0.45359237 kg; 1 lb = 16 oz. System: Imperial/US customary. Common SI comparison: 1 lb ≈ 453.59237 g.
Kilogram (kg) — SI base unit of mass. Defined by fixing the Planck constant h = 6.62607015×10⁻³⁴ J·s; all mass realizations are traceable to this constant. Relations used here: 1 kg = 2.20462262185 lb; 1 kg = 1000 g. System: SI.
Conversion formula
kg = lb × 0.45359237
lb = kg × 2.20462262185
Sources: NIST, Guide to the SI — Appendix B: Conversion Factors (exact 1 lb = 0.45359237 kg); BIPM, SI base unit — kilogram (definition by fixed Planck constant).
Conversion table
| lb | kg |
|---|---|
| 1 | 0.45359 |
| 2 | 0.90718 |
| 5 | 2.26796 |
| 10 | 4.53592 |
| 20 | 9.07185 |
| 25 | 11.33981 |
| 30 | 13.60777 |
| 40 | 18.14369 |
| 50 | 22.67962 |
| 75 | 34.01943 |
| 100 | 45.35924 |
| 150 | 68.03886 |
| 200 | 90.71847 |
| 250 | 113.39809 |
| 500 | 226.79619 |
| 750 | 340.19428 |
| 1000 | 453.59237 |
| 3000 | 1360.77711 |
| 5000 | 2267.96185 |
| 10000 | 4535.92370 |
Real-world examples (precise, standardized masses)
- US butter pack (net weight): 1 lb = 0.45359237 kg
- 25 lb dumbbell (labeled nominal): 25 lb = 11.33980925 kg
- Roll of US quarters (40 × 5.670 g): 0.5 lb = 0.2268 kg
- 1,000 US pennies, post-1982 (2.50 g each): 5.51155655 lb = 2.5 kg
- Ream of A4 paper, 80 g/m² (500 sheets): 5.50009252 lb = 2.5 kg
- World Athletics hammer (men): 16.00556023 lb = 7.26 kg
- World Athletics hammer (women): 8.81849049 lb = 4.0 kg
- World Athletics javelin (men): 1.76369810 lb = 0.8 kg
- World Athletics javelin (women): 1.32277357 lb = 0.6 kg
- Silver bar, 100 troy ounces (exact troy oz): 6.86 lb = 3.11 kg
What’s your scenario for using lb → kg? Need batch input, live two-way fields, or unit history notes? Tell us in the comments.
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