How many joules are in a BTU?

1,055.05585262 J, exactly, under the International Table definition this page converts with. It scales the way you would expect: 2 BTU is 2,110.11170524 J, 3 BTU is 3,165.16755786 J, 5 BTU is 5,275.2792631 J, 10 BTU is 10,550.5585262 J, 50 BTU is 52,752.792631 J, 100 BTU is 105,505.585262 J and 1,000 BTU is 1,055,055.85262 J. Half a BTU is 527.52792631 J and a million BTU is 1,055,055,852.62 J. Type any of those into the From box and the headline updates as you type.

Which BTU is this, since the definitions disagree?

The International Table BTU, fixed at exactly 1,055.05585262 J, which is the factor behind every figure on this page. NIST SP 811 footnote 9 states the exact factor as 1.05505585262 kJ. The rival definitions differ in the fourth digit: the thermochemical BTU is about 1,054.35 J, the 59 degree Fahrenheit BTU about 1,054.80 J, the 60 degree Fahrenheit BTU about 1,054.68 J, the mean BTU about 1,055.87 J and the 39 degree Fahrenheit BTU about 1,059.67 J. End to end that spread is about half a percent, and International Table against thermochemical is about 0.07 percent. The converter carries one BTU row and it is the International Table one, so a figure on another definition has to be worked out separately.

What is the formula for BTU to joules?

J = BTU x 1,055.05585262 going this way, and BTU = J / 1,055.05585262 going back, so 1 J is 0.000947817120313 BTU, 500 J is 0.473908560157 BTU, 1,000 J is 0.947817120313 BTU and 100,000 J is 94.7817120313 BTU. A kilojoule is that same division on a round number: 1 kJ is 0.947817120313 BTU. The swap button between the two boxes sets the reverse direction up for you, and 1,055.05585262 J comes back as exactly 1 BTU.

Worked example: how many joules is 12,000 BTU?

As an energy quantity, 12,000 International Table BTU displays as 12,660,670.2314 J, 12,660.6702314 kJ, 3,516.85284207 Wh or 3.51685284207 kWh. If a heating or cooling label instead specifies 12,000 BTU per hour, it names power: approximately 12,660,670.2314 joules per hour, or 3,516.85284207 watts. Wh per hour reduces to W; a watt hour by itself is energy. The converter menus contain energy units and do not infer a per-hour rate from a bare BTU value.

Why does the calorie row say 252.164400722 rather than 252?

Because the calorie in this converter is the thermochemical calorie, exactly 4.184 J, and 1,055.05585262 divided by 4.184 rounds to 252.164400722. The International Table BTU is itself built on the International Table calorie of 4.1868 J, and counted in those a BTU is about 251.996. That unit is not in the menu, so the cal and kcal rows here are thermochemical throughout: 1 BTU is 252.164400722 cal and 0.252164400722 kcal, and 100 BTU is 25,216.4400722 cal and 25.2164400722 kcal.

How many BTU is a kilowatt hour?

3,412.14163313 BTU, because a kilowatt hour is 3,600,000 J and a BTU is 1,055.05585262 J. A watt hour is a thousandth of that, 3.41214163313 BTU. Going the other way, 1 BTU is 0.293071070172 Wh and 0.000293071070172 kWh, and 100,000 BTU is 29.3071070172 kWh. All of those rows are on the page at the same time, so the watt hour figure doubles as a check on the joule figure.

How is the answer rounded and copied?

The arithmetic runs on the number you typed and only the display is rounded, to twelve significant digits with trailing zeros dropped, which is why 1 BTU reads 1,055.05585262 J and not 1,055.056. Digits are grouped with commas for reading, and Copy result copies the plain figure without them so it pastes into a spreadsheet. Magnitudes below a millionth, or at a thousand trillion and above, switch to exponential form: turn on Show 1 more in the readout and 1 BTU also appears as 6.58514067819e21 eV. The From box accepts a single decimal or scientific number and a matching unit suffix, so 1e3, 1,000 and 1,000 BTU are accepted. Thousands must be properly grouped; 1,5 is refused as a decimal comma. Fractions and compound measurements are refused. An empty box says Type a number and produces no numeric result. Input magnitude must be finite, with at most 512 significant digits; nonzero underflow is refused.

Why does the page open on BTU and joules when I last converted something else?

This focused page opens on British thermal unit and Joule, while preserving the main converter’s saved unit pair. When browser storage is usable, a saved value and uncommon-unit preference can travel between pages. The value’s suffix must still match the current From unit. Valid deliberate scalar edits can save those fields after a short delay; invalid or incomplete drafts do not overwrite the saved record. Unusable or conflicting records are kept with an explanation until you use Forget saved settings, which keeps the current conversion on screen.

BTU to Joules Converter

A BTU is 1,055.05585262 joules, so BTU to joules is one multiplication: J = BTU x 1,055.05585262. That makes 10 BTU 10,550.5585262 J, 100 BTU 105,505.585262 J and 1,000 BTU 1,055,055.85262 J. The factor is the International Table BTU, defined as exactly 1,055.05585262 J in NIST SP 811 footnote 9, and it is the only BTU in the menu: the thermochemical BTU of about 1,054.35 J and the 39 degree Fahrenheit BTU of about 1,059.67 J differ in the fourth digit, and neither is what this page returns. The page opens with British thermal unit in the From box and Joule in the To box, ahead of whatever pair the converter last remembered, and it answers while you type to twelve significant digits. Under the headline the same energy appears in kilojoules, calories, kilocalories, watt hours and kilowatt hours at once, so 1 BTU reads 1.05505585262 kJ, 252.164400722 cal, 0.252164400722 kcal, 0.293071070172 Wh and 0.000293071070172 kWh on one screen. The swap button between the two boxes turns the page into a joules to BTU converter without a reload.

From

To1,055.05585262

Category: Energy

Base unit: joule

Uncommon units: Show 1 more

BTU uses the International Table definition (1,055.05585262 J); cal and kcal are thermochemical (4.184 J per cal). Wh and kWh are energy, not power in W or kW.

Results round to 12 significant digits using the listed unit definitions. Input must have a finite numeric magnitude and at most 512 significant digits. Type a single decimal or scientific number; a matching From unit suffix is accepted. Commas and grouped spaces separate thousands; decimal commas, fractions and compound measurements are refused.

1 BTU in every energy unit

JouleJ
1,055.05585262
KilojoulekJ
1.05505585262
Caloriecal
252.164400722
Kilocaloriekcal
0.252164400722
Watt hourWh
0.293071070172
Kilowatt hourkWh
0.000293071070172

Selectable complete conversion

Unit Converter — Energy
Input: 1 (British thermal unit, BTU)
Result: 1055.05585262 J (Joule)
Displayed values round to 12 significant digits.
BTU uses the International Table definition (1,055.05585262 J); cal and kcal are thermochemical (4.184 J per cal). Wh and kWh are energy, not power in W or kW.
All other units:
Joule (J): 1055.05585262
Kilojoule (kJ): 1.05505585262
Calorie (cal): 252.164400722
Kilocalorie (kcal): 0.252164400722
Watt hour (Wh): 0.293071070172
Kilowatt hour (kWh): 0.000293071070172
Electronvolt (eV): 6.58514067819e21

Common questions

How many joules are in a BTU?: 1,055.05585262 J, exactly, under the International Table definition this page converts with. It scales the way you would expect: 2 BTU is 2,110.11170524 J, 3 BTU is 3,165.16755786 J, 5 BTU is 5,275.2792631 J, 10 BTU is 10,550.5585262 J, 50 BTU is 52,752.792631 J, 100 BTU is 105,505.585262 J and 1,000 BTU is 1,055,055.85262 J. Half a BTU is 527.52792631 J and a million BTU is 1,055,055,852.62 J. Type any of those into the From box and the headline updates as you type.
Which BTU is this, since the definitions disagree?: The International Table BTU, fixed at exactly 1,055.05585262 J, which is the factor behind every figure on this page. NIST SP 811 footnote 9 states the exact factor as 1.05505585262 kJ. The rival definitions differ in the fourth digit: the thermochemical BTU is about 1,054.35 J, the 59 degree Fahrenheit BTU about 1,054.80 J, the 60 degree Fahrenheit BTU about 1,054.68 J, the mean BTU about 1,055.87 J and the 39 degree Fahrenheit BTU about 1,059.67 J. End to end that spread is about half a percent, and International Table against thermochemical is about 0.07 percent. The converter carries one BTU row and it is the International Table one, so a figure on another definition has to be worked out separately.
What is the formula for BTU to joules?: J = BTU x 1,055.05585262 going this way, and BTU = J / 1,055.05585262 going back, so 1 J is 0.000947817120313 BTU, 500 J is 0.473908560157 BTU, 1,000 J is 0.947817120313 BTU and 100,000 J is 94.7817120313 BTU. A kilojoule is that same division on a round number: 1 kJ is 0.947817120313 BTU. The swap button between the two boxes sets the reverse direction up for you, and 1,055.05585262 J comes back as exactly 1 BTU.
Worked example: how many joules is 12,000 BTU?: As an energy quantity, 12,000 International Table BTU displays as 12,660,670.2314 J, 12,660.6702314 kJ, 3,516.85284207 Wh or 3.51685284207 kWh. If a heating or cooling label instead specifies 12,000 BTU per hour, it names power: approximately 12,660,670.2314 joules per hour, or 3,516.85284207 watts. Wh per hour reduces to W; a watt hour by itself is energy. The converter menus contain energy units and do not infer a per-hour rate from a bare BTU value.
Why does the calorie row say 252.164400722 rather than 252?: Because the calorie in this converter is the thermochemical calorie, exactly 4.184 J, and 1,055.05585262 divided by 4.184 rounds to 252.164400722. The International Table BTU is itself built on the International Table calorie of 4.1868 J, and counted in those a BTU is about 251.996. That unit is not in the menu, so the cal and kcal rows here are thermochemical throughout: 1 BTU is 252.164400722 cal and 0.252164400722 kcal, and 100 BTU is 25,216.4400722 cal and 25.2164400722 kcal.
How many BTU is a kilowatt hour?: 3,412.14163313 BTU, because a kilowatt hour is 3,600,000 J and a BTU is 1,055.05585262 J. A watt hour is a thousandth of that, 3.41214163313 BTU. Going the other way, 1 BTU is 0.293071070172 Wh and 0.000293071070172 kWh, and 100,000 BTU is 29.3071070172 kWh. All of those rows are on the page at the same time, so the watt hour figure doubles as a check on the joule figure.
How is the answer rounded and copied?: The arithmetic runs on the number you typed and only the display is rounded, to twelve significant digits with trailing zeros dropped, which is why 1 BTU reads 1,055.05585262 J and not 1,055.056. Digits are grouped with commas for reading, and Copy result copies the plain figure without them so it pastes into a spreadsheet. Magnitudes below a millionth, or at a thousand trillion and above, switch to exponential form: turn on Show 1 more in the readout and 1 BTU also appears as 6.58514067819e21 eV. The From box accepts a single decimal or scientific number and a matching unit suffix, so 1e3, 1,000 and 1,000 BTU are accepted. Thousands must be properly grouped; 1,5 is refused as a decimal comma. Fractions and compound measurements are refused. An empty box says Type a number and produces no numeric result. Input magnitude must be finite, with at most 512 significant digits; nonzero underflow is refused.
Why does the page open on BTU and joules when I last converted something else?: This focused page opens on British thermal unit and Joule, while preserving the main converter’s saved unit pair. When browser storage is usable, a saved value and uncommon-unit preference can travel between pages. The value’s suffix must still match the current From unit. Valid deliberate scalar edits can save those fields after a short delay; invalid or incomplete drafts do not overwrite the saved record. Unusable or conflicting records are kept with an explanation until you use Forget saved settings, which keeps the current conversion on screen.

Results round to 12 significant digits using the listed unit conventions. Many factors are exact definitions; psi and parsec use rounded coefficients. Temperature includes scale offsets. Days and weeks are fixed-duration units, and unit conversion does not determine calendar dates, ambient pressure or a software label’s convention.