Specific energy
Kilojoules per kilogram to BTU per pound
kJ/kg → BTU/lb
1,000 kJ/kg = 429.92 BTU/lb
BTU per pound to kilojoules per kilogram
BTU/lb → kJ/kg
20,000 BTU/lb = 46,520 kJ/kg
Megajoules per kilogram to kilowatt-hours per kilogram
MJ/kg → kWh/kg
46 MJ/kg = 12.78 kWh/kg
Kilowatt-hours per kilogram to megajoules per kilogram
kWh/kg → MJ/kg
12.8 kWh/kg = 46.08 MJ/kg
Watt-hours per kilogram to kilojoules per kilogram
Wh/kg → kJ/kg
250 Wh/kg = 900 kJ/kg
Kilocalories per kilogram to kilojoules per kilogram
kcal/kg → kJ/kg
1,000 kcal/kg = 4,184 kJ/kg
Specific energy units at a glance
| Unit | Symbol | In joules per kilogram | Defined as |
|---|---|---|---|
| Joule per kilogram | J/kg | 1 | SI |
| Kilojoule per kilogram | kJ/kg | 1,000 | 1,000 J/kg |
| Megajoule per kilogram | MJ/kg | 1,000,000 | 1,000 kJ/kg |
| BTU per pound | BTU/lb | 2,326 | 2.326 kJ/kg |
| Kilocalorie per kilogram | kcal/kg | 4,184 | 1 cal/g |
| Watt-hour per kilogram | Wh/kg | 3,600 | 3.6 kJ/kg |
| Kilowatt-hour per kilogram | kWh/kg | 3,600,000 | 3.6 MJ/kg |
Gasoline holds about 46 MJ/kg (12.8 kWh/kg); a lithium-ion battery about 250 Wh/kg.