A contractor says our AC is 12,000 BTU. What's that in kJ?

12,000 × 1.055 = 12,660 kJ. If you're comparing with a European unit rated in kilowatts, divide by 3.6: 12,660 ÷ 3.6 = 3.5 kW.

Why do US HVAC systems use BTU instead of kJ?

Tradition and market. BTU has been the standard in North America for over a century. International equipment increasingly lists both BTU and kJ.

My energy audit report says 250,000 BTU/h. How do I convert to kJ for the international office?

Multiply by 1.055: 250,000 × 1.055 = 263,750 kJ/h. Round to 264 kJ/h for the report.

Is 1 BTU always 1.055 kJ, or does it vary?

BTU (IT) = exactly 1.055056 kJ by definition. There's also BTU (thermochemical) = 1.054 kJ, but IT is standard for HVAC. Also see [BTU to Joules](/energy/btu-to-joules/).

BTU (IT) to Kilojoule Converter

Enter a value to instantly convert between energy units.

From

Precision4 dp

1 BTU (IT) = 1.0551 Kilojoule

Key Formulas

Kilocalorie → Kilojoule

kJ = kcal × 4.184

Kilojoule → Kilocalorie

kcal = kJ × 0.239006

Kilowatt-Hour → Joule

J = kWh × 3600000

Joule → Kilowatt-Hour

kWh = J × 2.77778e-7

Formula

kJ = BTU × 1.055056

One BTU (British Thermal Unit, IT) equals 1.055 kilojoules. BTU measures heating and cooling capacity for US HVAC equipment (air conditioners, furnaces, heat pumps). Kilojoules are the SI standard used in international building codes and energy audits. Converting BTU to kJ is essential when specifying equipment internationally or comparing energy efficiency across markets.

Source: NIST SP 811, Table B.8

Frequently Asked Questions

Real-World Examples

A typical 12,000 BTU air conditioner (1 ton of cooling) delivers 12.7 kJ — common size for small bedrooms in the US.

12000 BTU = 12660.67 kJ

A central air unit rated 60,000 BTU/h provides 63.3 kJ/h heating or cooling — standard for whole-house systems.

60000 BTU = 63303.36 kJ

A commercial boiler rated 250,000 BTU/h generates 264 kJ/h for large building heating — used in energy audit reports.

250000 BTU = 263680.14 kJ

Definition. 1 BTU (IT) = exactly 1.055056 kJ, by scientific definition.

1 BTU = 1.055 kJ

kcal to kj kj to kcal kwh to joules joules to kwh btu to joules calories to joules

BTU (IT) to Kilojoule Converter

Key Formulas

Formula

Frequently Asked Questions

Real-World Examples

Related Converters