Unit converter
Specific energy.
Convert Wh/kg to kJ/kg, or pick any of the 6 units in the menus. Type in either box and the other follows. Energy per unit mass, from fuels to foods to the watt-hours per kilogram a battery manages.
| Wh/kg | kJ/kg |
|---|---|
| 1 Wh/kg | 3.6 kJ/kg |
| 2 Wh/kg | 7.2 kJ/kg |
| 3 Wh/kg | 10.8 kJ/kg |
| 4 Wh/kg | 14.4 kJ/kg |
| 5 Wh/kg | 18 kJ/kg |
| 10 Wh/kg | 36 kJ/kg |
| 15 Wh/kg | 54 kJ/kg |
| 20 Wh/kg | 72 kJ/kg |
| 25 Wh/kg | 90 kJ/kg |
| 50 Wh/kg | 180 kJ/kg |
| 75 Wh/kg | 270 kJ/kg |
| 100 Wh/kg | 360 kJ/kg |
| 250 Wh/kg | 900 kJ/kg |
| 500 Wh/kg | 1800 kJ/kg |
| 1000 Wh/kg | 3600 kJ/kg |
- Every unit in the menus is defined against J/kg, so any pairing converts by the same single route.
Definitions
- Watt-hours per kilogram is how battery energy density is quoted. A current lithium-ion cell manages roughly 250 Wh/kg.
- Kilojoules per kilogram measures energy content by mass, from fuels to foods.
- Every unit here is defined against the J/kg.
- Every unit in the menus is exact by definition, so the only rounding on this page is the one you choose for the display.
How it works
Every value is converted into joule per kilograms and then back out into the unit you asked for. One route covers every pairing in the menus, so an unusual combination is no less accurate than a common one, and adding a unit affects only that unit.
Both boxes are live. Whichever one you last typed in is the source, changing either menu recalculates straight away, and Swap exchanges the units and the values so the number you are reading stays where you are looking.
Display precision sets a maximum number of significant figures and trims trailing zeroes, so it changes what you see and never what was calculated. The editable box always holds a plain number at full working precision, so you can carry on from either side.
Common questions this answers: how many kilojoules per kilogram in a watt-hour per kilogram (3.6), how many watt-hours per kilogram in a kilojoule per kilogram (0.277778), and what 100 Wh/kg is in kilojoules per kilogram (360 kJ/kg).
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- Works offline once loaded
From the maker of Ans — a scientific calculator you can own. Same idea: a proper instrument, nothing in the way.