How many BTU are in one joule?

One joule equals 0.000947817 BTU (thermochemical). Conversely, 1 BTU = 1,055.05585 J.

Which BTU definition does this tool use?

This tool uses the thermochemical BTU (BTU_th), where 1 BTU = 1,055.05585262 J. This is the most common definition in physics and chemistry. The International Table BTU (1 BTU = 1,055.05585 J) differs by less than 0.001% and is treated as identical here.

How do I convert kilojoules to BTU?

Multiply your kJ value by 0.947817 to get BTU. For example, 10 kJ = 9.47817 BTU. You can also type directly into the kJ field in this tool.

What is BTU per hour (BTU/hr)?

BTU/hr is a unit of power (energy per unit time) common in HVAC. This tool shows the BTU/hr equivalent when you treat your joule input as energy delivered in one hour, i.e., BTU/hr = J / 3600 × (1 J = 0.000947817 BTU) × 3600 = BTU value directly — but as a power rate it means: power in watts = BTU/hr ÷ 3.41214. Use the reference row for context.

Why does my HVAC rating use BTU?

The US building and HVAC industry historically used imperial units. Air conditioner capacity is rated in BTU/hr (often just called "BTU"), while the rest of the world uses watts or kilowatts. 1 watt = 3.41214 BTU/hr.

Joules to BTU Converter

Name: Joules to BTU Converter
Availability: InStock
Author: Nham Vu

Enter joules or BTU for instant bidirectional conversion. Also converts kilojoules and shows BTU/hr equivalent.

Joules ↔ BTU Converter

Joules (J)

Kilojoules (kJ)

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BTU (thermochemical)

BTU

1 BTU = 1,055.05585 J (thermochemical)

Quick Reference Table

Common joule values in BTU (1 J = 0.000947817 BTU)

Joules (J)	kJ	BTU

1 BTU = 1,055.05585 J — thermochemical definition

BTU/hr (power) reference

HVAC equipment ratings use BTU/hr (energy per hour), not BTU alone. 1 watt = 3.41214 BTU/hr exactly. To convert watts to BTU/hr, multiply by 3.41214. To convert BTU/hr to watts, divide by 3.41214. A 1,000 W heater outputs 3,412 BTU/hr; a 12,000 BTU/hr air conditioner uses about 3,517 W.

Summary