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Joules to BTU Converter
↔ Convert BTU to J instead

Common Conversions

J BTU
100 0.0948
500 0.4739
1000 0.9478
1055.06 1
5000 4.739
10000 9.478
50000 47.39
100000 94.78
500000 473.9
1000000 947.8
3600000 3412.1

Why this conversion matters in chemistry

Calorimetry and reaction enthalpies in a chemistry lab come out in joules. A BTU is what happens when those same numbers meet a US building-energy calculation or a heat-exchanger duty on a process diagram. One BTU is defined as the energy needed to raise a pound of water by one degree Fahrenheit, and it works out to 1055.06 J. A 200 J/g phase change in a DSC trace becomes about 86 BTU/lb when the same material's latent heat is specified for a thermal-storage application. Multiplying by 0.000947817 is the step that lets the two industries trade numbers without talking past each other.

Formula

BTU = J × 0.000947817

Worked Examples

1055.06 J = 1 BTU

The definition itself — one BTU is the heat needed to raise one pound of water by one degree Fahrenheit.

1000 J = 0.9478 BTU

One kilojoule, the energy released by a mid-sized organic reaction at the millimole scale.

4184 J = 3.966 BTU

One kilocalorie — the Calorie of food labels — expressed in BTU terms.

100000 J = 94.78 BTU

100 kJ — roughly the heat released by burning 4.4 g of methanol at its standard combustion enthalpy of about 22.7 kJ per gram. A useful midscale reference when scaling up.

Frequently Asked Questions

How do I convert joules to BTU?
Multiply by 0.000947817. So 1055.06 J is exactly 1 BTU, and 1 kJ is about 0.948 BTU — handy for sanity-checking an energy figure on the fly.
What is a BTU?
A British thermal unit is the energy needed to raise one pound of water by one degree Fahrenheit at a specified reference temperature. The IT BTU used in most tables is 1055.06 J exactly.
When does a chemist actually need BTU?
Anywhere chemistry meets US-spec heat engineering — process heat duties, combustion of fuels, HVAC calculations for a lab building, or rating the output of a burner or boiler. Reaction energies have to land in BTU before those calculations accept them.
How does BTU compare to calories?
One BTU is about 252.164 thermochemical calories, or 0.252 kcal. One BTU is also about 1.055 kJ — the three numbers together cover most of the cross-talk between reaction calorimetry and engineering heat units.