Frequently Asked Questions — kWh/kg to MJ/kg
Question: How many MJ/kg is 1 kWh/kg?
Answer: 1 kWh/kg = 3.6 MJ/kg exactly. Since 1 kilowatt-hour = 3.6 megajoules, 1 kWh/kg = 3.6 MJ/kg.
Question: How do I convert kWh/kg to MJ/kg?
Answer: Multiply the value in kWh/kg by 3.6. For example, a Li-ion battery at 0.25 kWh/kg × 3.6 = 0.9 MJ/kg.
Question: What is the reverse conversion — MJ/kg to kWh/kg?
Answer: 1 MJ/kg = 0.2778 kWh/kg. Divide MJ/kg by 3.6 to get kWh/kg.
Question: What is a typical kWh/kg value for a lithium-ion battery?
Answer: Current lithium-ion batteries achieve 0.1–0.3 kWh/kg (0.36–1.08 MJ/kg). Solid-state batteries aim for 0.5+ kWh/kg. For comparison, gasoline is about 12.2 kWh/kg (43.9 MJ/kg) — around 40–50× more energy dense by mass.
Question: Why convert between kWh/kg and MJ/kg?
Answer: kWh/kg is commonly used in electrical engineering and battery technology; MJ/kg is used in thermodynamics and combustion engineering. Converting between them allows direct comparison of chemical fuels (MJ/kg) and battery systems (kWh/kg) on equal footing.