Skip to main content

Frequently Asked Questions — kJ/kg to Btu/lb

Question: How many Btu/lb is 1 kJ/kg?

Answer: 1 kJ/kg = 0.4299226139 Btu (IT)/lb. Multiply kilojoules per kilogram by 0.4299226139 to get BTU per pound.

Question: How do I convert kJ/kg to Btu/lb?

Answer: Multiply the value in kJ/kg by 0.4299226139. For example, 10 kJ/kg × 0.4299226139 = 4.299226139 Btu/lb.

Question: What is the reverse conversion — Btu/lb to kJ/kg?

Answer: 1 Btu (IT)/lb = 2.326 kJ/kg. Multiply Btu/lb by 2.326 to get kJ/kg.

Question: What is kJ/kg used for?

Answer: kJ/kg (kilojoule per kilogram) is the SI unit for specific energy or heating value of a fuel. It measures how much energy is released per kilogram of fuel burned. Common use cases include comparing fuels like natural gas (~55,000 kJ/kg), gasoline (~44,000–46,000 kJ/kg), and coal (~24,000–35,000 kJ/kg).

Question: Why are Btu/lb and kJ/kg both used?

Answer: Btu/lb is traditional in the US energy industry (natural gas, coal, oil). kJ/kg is the SI standard used in science, engineering, and most of the world. Both express the same physical quantity — specific energy — with a fixed conversion factor of 1 Btu/lb = 2.326 kJ/kg.