La masa es la cantidad de materia en un cuerpo físico.Es una propiedad fundamental de la materia y se mide en kilogramos (kg).
1 lb = 0.454 kg 
1 kg = 2.205 lb 
Ejemplo: 
Convertir 15 Libra a Kilogramo:
15 lb = 6.804 kg 
| Libra | Kilogramo | 
|---|---|
| 0.01 lb | 0.005 kg | 
| 0.1 lb | 0.045 kg | 
| 1 lb | 0.454 kg | 
| 2 lb | 0.907 kg | 
| 3 lb | 1.361 kg | 
| 5 lb | 2.268 kg | 
| 10 lb | 4.536 kg | 
| 20 lb | 9.072 kg | 
| 30 lb | 13.608 kg | 
| 40 lb | 18.144 kg | 
| 50 lb | 22.68 kg | 
| 60 lb | 27.216 kg | 
| 70 lb | 31.751 kg | 
| 80 lb | 36.287 kg | 
| 90 lb | 40.823 kg | 
| 100 lb | 45.359 kg | 
| 250 lb | 113.398 kg | 
| 500 lb | 226.796 kg | 
| 750 lb | 340.194 kg | 
| 1000 lb | 453.592 kg | 
| 10000 lb | 4,535.924 kg | 
| 100000 lb | 45,359.237 kg |