Energy Reference Sheet
Common units: joules (J), kilojoules (kJ), watt-hours (Wh), kilowatt-hours (kWh), calories (cal), kilocalories (kcal), BTU, foot-pounds (ft·lbf), electronvolts (eV).
Conversions
Metric (SI)
- 1 kilojoule (kJ) = 1,000 J
- 1 megajoule (MJ) = 1,000,000 J
- 1 gigajoule (GJ) = 1,000,000,000 J
- 1 Wh = 3,600 J · 1 kWh = 3.6×10⁶ J · 1 MWh = 3.6×10⁹ J
Practical units
- 1 calorie (cal) ≈ 4.184 J · 1 kilocalorie (kcal) ≈ 4,184 J
- 1 BTU (IT) ≈ 1,055.056 J
- 1 foot-pound (ft·lbf) ≈ 1.35582 J
- 1 eV = 1.602176634×10⁻¹⁹ J
Quick benchmarks
- AA battery (typ.): ~3 Wh ≈ 10.8 kJ
- Food label “calorie” = 1 kcal ≈ 4.184 kJ
- 1 kWh (home electricity) = 3.6 MJ
Common units (in J)
| Unit | Symbol | In J |
|---|---|---|
| Joule | J | 1 |
| Kilojoule | kJ | 1,000 |
| Megajoule | MJ | 1,000,000 |
| Gigajoule | GJ | 1,000,000,000 |
| Watt-hour | Wh | 3,600 |
| Kilowatt-hour | kWh | 3,600,000 |
| Megawatt-hour | MWh | 3,600,000,000 |
| Calorie (thermochemical) | cal | 4.184 |
| Kilocalorie | kcal | 4,184 |
| British thermal unit (IT) | BTU | 1,055.056 |
| Foot-pound | ft·lbf | 1.35582 |
| Electronvolt | eV | 1.602176634×10⁻¹⁹ |