Kilojoules (kJ) to Watt-Hours (Wh) Converter
Enter a value to instantly convert between energy units.
1 Kilojoule = 0.2778 Watt-Hour
Key Formulas
Kilocalorie → Kilojoule
kJ = kcal × 4.184Kilojoule → Kilocalorie
kcal = kJ × 0.239006Kilowatt-Hour → Joule
J = kWh × 3600000Joule → Kilowatt-Hour
kWh = J × 2.77778e-7Formula
Wh = kJ ÷ 3.6Watt-hours measure electrical energy in smaller scales than kilowatt-hours — they're more readable for portable devices. A smartphone battery might have 15 Wh (54 kJ); a power bank might have 26 Wh (94 kJ). Kilojoules are the SI standard, but watt-hours are conventional in consumer electronics specs. You use this conversion when comparing battery capacities across product datasheets, understanding device runtime, or calculating total energy in a portable system.
Source: NIST SP 811, Table B.8
Frequently Asked Questions
Real-World Examples
A smartphone designer checking battery capacity: 3.6 kJ (1 Wh) = the energy for one watt of output for one hour. A typical phone battery is 15–20 Wh or 54–72 kJ.
3.6 kJ = 1 Wh
A consumer comparing power banks. Spec sheet lists 15 Wh capacity (54 kJ) — enough to charge a phone once. At 5V output, that's ~3,000 mAh (milliamp-hours).
54 kJ = 15 Wh
An emergency kit planner. A 60 Wh solar charger (216 kJ) can recharge a laptop (50 Wh battery) once, or a phone (15 Wh) four times over a sunny day.
216 kJ = 60 Wh
A camping enthusiast choosing a portable battery. A 10 Wh unit (36 kJ) runs an LED lamp (~5W) for 2 hours, or charges a phone partially. Compact and lightweight for backpacking.
36 kJ = 10 Wh