How many calories is 1 joule?

0.239005736138 cal, because a thermochemical calorie is exactly 4.184 joules and the division does not come out even. It scales the way you would expect: 10 J is 2.39005736138 cal, 20 J is 4.78011472275 cal, 50 J is 11.9502868069 cal, 100 J is 23.9005736138 cal, 500 J is 119.502868069 cal and 1,000 J is 239.005736138 cal. The one round number in the pair runs the other way: 4,184 J is exactly 1,000 cal. Type any of these into the From box and the headline updates while you type.

Is this the small calorie or the food Calorie?

The menu’s Calorie (cal) is the small thermochemical calorie, exactly 4.184 J. Its Kilocalorie (kcal) is exactly 1,000 of those, or 4,184 J. A food Calorie commonly means a kilocalorie, but source labels and calorie conventions must be checked rather than inferred from capitalization or subject alone. Here 1,000 J displays as 239.005736138 cal and 0.239005736138 kcal, while 1 J gives 0.000239005736138 kcal. Both output rows are available together. Neither the food/physics context nor the converter establishes which definition an external source intended.

What is the formula, and is the 4.184 factor exact?

cal = J / 4.184 going this way, and J = cal x 4.184 going back. The factor is exact by definition rather than measured: the thermochemical calorie is defined as exactly 4.184 joules, and the kilocalorie as exactly 4,184 joules. So 1 cal is 4.184 J, 10 cal is 41.84 J, 100 cal is 418.4 J and 1,000 cal is 4,184 J, all exactly. The only rounding on this page is in the printing: an answer like 0.239005736138 cal is 1 / 4.184 cut to twelve significant digits, not an approximation of the factor.

Why do some tables say a calorie is 4.1868 joules?

This converter uses the thermochemical calorie of exactly 4.184 J and its kilocalorie of exactly 4,184 J. The International Table calorie is a different definition, exactly 4.1868 J. The IT definition is about 0.067% larger: 1,000 J displays as 239.005736138 thermochemical calories, compared with 238.845896627 IT calories. Other historical calorie definitions also exist. IT and temperature-specific calories are absent from the menu; for an explicitly supplied IT-calorie convention, divide the original joules by exactly 4.1868 separately rather than reading this cal row.

How is the result rounded?

Decimal-rational arithmetic preserves the written input and exact definitions, then displayed and copied results round to twelve significant digits with trailing zeros dropped. Thus 1 J reads 0.239005736138 cal, and 1,000,000 J displays as 239,005.736138 cal. Very large or very small displayed magnitudes use exponential form at the same precision: with uncommon units shown, 1 J reads 6.24150907446e18 eV using the exact SI electronvolt of 1.602176634e-19 J. Properly grouped numbers, decimal points, signs, exponents and matching suffixes are accepted; malformed commas, fractions and compound quantities are refused. Copy result copies the displayed headline without digit-grouping commas; each visible conversion row has its own Copy button. Displayed and copied values round to twelve significant digits. If native copying fails, a complete selectable summary identifies the input, selected pair and conventions and includes every unit in the category, including uncommon units.

How do I convert calories back to joules?

Press Swap units to reverse the selected pair, or multiply thermochemical calories by exactly 4.184. Thus 1 cal is exactly 4.184 J, 100 cal exactly 418.4 J and 1,000 cal exactly 4,184 J. Entering the previously rounded 239.005736138 cal displays as 1,000 J after rounding; its exact supplied-input value is 1000.000000001392 J. For a stated thermochemical kilocalorie quantity choose Kilocalorie (kcal): 100 kcal is 418,400 J or 418.4 kJ, and 2,000 kcal is 8,368,000 J or 8,368 kJ.

What else is shown beside the calorie figure?

The other common energy units appear for the amount you typed, with the electronvolt available through Show 1 more. Calories and kilocalories use the thermochemical convention, and BTU uses the International Table convention. For 1,000 J that is 1 kJ, 239.005736138 cal, 0.239005736138 kcal, 0.277777777778 Wh, 0.000277777777778 kWh and 0.947817120313 BTU. Two of those are handy checks on the calorie figure: 1 Wh is 3,600 J and 860.420650096 cal, and 1 IT BTU is exactly 1,055.05585262 J and displays as 252.164400722 thermochemical cal. The electronvolt is hidden until you turn on Show 1 more in the readout, and can be chosen as a target.

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

This focused page opens on Joule and Calorie, while preserving the main converter’s saved unit pair. When storage is usable, a saved value and uncommon-unit preference can travel between pages. Its suffix must still match From. Valid deliberate scalar edits can save those fields after a short delay; invalid or incomplete drafts preserve the saved record. Unusable or conflicting records remain until you use Forget saved settings, which keeps the current conversion on screen. Your input and converted values are calculated in the browser and are not uploaded by the converter. The definitions arrive with the page, so conversion needs no external data lookup and keeps working offline after the page has loaded. The core conversion needs no account.

Joules to Calories Converter

One thermochemical calorie is exactly 4.184 joules, so joules to calories is a single division: cal = J / 4.184. That makes 1 J read 0.239005736138 cal, 1,000 J read 239.005736138 cal, and 4,184 J come back as exactly 1,000 cal. The calorie in the To box is the small thermochemical calorie. A food Calorie commonly means a kilocalorie, represented here by the thermochemical kilocalorie of exactly 4,184 J; check your source’s stated convention. Thus 1,000 J is 239.005736138 cal but only 0.239005736138 kcal. This page opens the converter on joules into calories whatever pair you converted last, answers as you type with no button to press, and prints twelve significant digits so the figure is checkable rather than rounded to three. Under the answer the same energy is listed in the other common energy units, using thermochemical calories and IT British thermal units at the same time, with the electronvolt behind the switch marked Show 1 more.

From

To0.239005736138

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 J in every energy unit

KilojoulekJ
0.001
Caloriecal
0.239005736138
Kilocaloriekcal
0.000239005736138
Watt hourWh
0.000277777777778
Kilowatt hourkWh
2.77777777778e-7
British thermal unitBTU
0.000947817120313

Selectable complete conversion

Unit Converter — Energy
Input: 1 (Joule, J)
Result: 0.239005736138 cal (Calorie)
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:
Kilojoule (kJ): 0.001
Calorie (cal): 0.239005736138
Kilocalorie (kcal): 0.000239005736138
Watt hour (Wh): 0.000277777777778
Kilowatt hour (kWh): 2.77777777778e-7
British thermal unit (BTU): 0.000947817120313
Electronvolt (eV): 6.24150907446e18

Joules in thermochemical calories, kilocalories and kilojoules

Each row is calculated directly from its original joules under the thermochemical definition: calories round to four decimal places and kilocalories to six. Kilojoules use the exact factor 1/1,000. In particular, 4.184 J = 1 cal and 4,184 J = 1 kcal exactly.

Joules	Thermochemical calories (cal)	Thermochemical kilocalories (kcal)	Kilojoules (kJ)
0.5 J	0.1195	0.000120	0.0005
1 J	0.2390	0.000239	0.001
4.184 J	1.0000	0.001000	0.004184
5 J	1.1950	0.001195	0.005
10 J	2.3901	0.002390	0.01
20 J	4.7801	0.004780	0.02
50 J	11.9503	0.011950	0.05
100 J	23.9006	0.023901	0.1
250 J	59.7514	0.059751	0.25
500 J	119.5029	0.119503	0.5
1,000 J	239.0057	0.239006	1
2,000 J	478.0115	0.478011	2
3,600 J	860.4207	0.860421	3.6
4,184 J	1,000.0000	1.000000	4.184
5,000 J	1,195.0287	1.195029	5
10,000 J	2,390.0574	2.390057	10
100,000 J	23,900.5736	23.900574	100
1,000,000 J	239,005.7361	239.005736	1,000
3,600,000 J	860,420.6501	860.420650	3,600

Common questions

How many calories is 1 joule?: 0.239005736138 cal, because a thermochemical calorie is exactly 4.184 joules and the division does not come out even. It scales the way you would expect: 10 J is 2.39005736138 cal, 20 J is 4.78011472275 cal, 50 J is 11.9502868069 cal, 100 J is 23.9005736138 cal, 500 J is 119.502868069 cal and 1,000 J is 239.005736138 cal. The one round number in the pair runs the other way: 4,184 J is exactly 1,000 cal. Type any of these into the From box and the headline updates while you type.
Is this the small calorie or the food Calorie?: The menu’s Calorie (cal) is the small thermochemical calorie, exactly 4.184 J. Its Kilocalorie (kcal) is exactly 1,000 of those, or 4,184 J. A food Calorie commonly means a kilocalorie, but source labels and calorie conventions must be checked rather than inferred from capitalization or subject alone. Here 1,000 J displays as 239.005736138 cal and 0.239005736138 kcal, while 1 J gives 0.000239005736138 kcal. Both output rows are available together. Neither the food/physics context nor the converter establishes which definition an external source intended.
What is the formula, and is the 4.184 factor exact?: cal = J / 4.184 going this way, and J = cal x 4.184 going back. The factor is exact by definition rather than measured: the thermochemical calorie is defined as exactly 4.184 joules, and the kilocalorie as exactly 4,184 joules. So 1 cal is 4.184 J, 10 cal is 41.84 J, 100 cal is 418.4 J and 1,000 cal is 4,184 J, all exactly. The only rounding on this page is in the printing: an answer like 0.239005736138 cal is 1 / 4.184 cut to twelve significant digits, not an approximation of the factor.
Why do some tables say a calorie is 4.1868 joules?: This converter uses the thermochemical calorie of exactly 4.184 J and its kilocalorie of exactly 4,184 J. The International Table calorie is a different definition, exactly 4.1868 J. The IT definition is about 0.067% larger: 1,000 J displays as 239.005736138 thermochemical calories, compared with 238.845896627 IT calories. Other historical calorie definitions also exist. IT and temperature-specific calories are absent from the menu; for an explicitly supplied IT-calorie convention, divide the original joules by exactly 4.1868 separately rather than reading this cal row.
How is the result rounded?: Decimal-rational arithmetic preserves the written input and exact definitions, then displayed and copied results round to twelve significant digits with trailing zeros dropped. Thus 1 J reads 0.239005736138 cal, and 1,000,000 J displays as 239,005.736138 cal. Very large or very small displayed magnitudes use exponential form at the same precision: with uncommon units shown, 1 J reads 6.24150907446e18 eV using the exact SI electronvolt of 1.602176634e-19 J. Properly grouped numbers, decimal points, signs, exponents and matching suffixes are accepted; malformed commas, fractions and compound quantities are refused. Copy result copies the displayed headline without digit-grouping commas; each visible conversion row has its own Copy button. Displayed and copied values round to twelve significant digits. If native copying fails, a complete selectable summary identifies the input, selected pair and conventions and includes every unit in the category, including uncommon units.
How do I convert calories back to joules?: Press Swap units to reverse the selected pair, or multiply thermochemical calories by exactly 4.184. Thus 1 cal is exactly 4.184 J, 100 cal exactly 418.4 J and 1,000 cal exactly 4,184 J. Entering the previously rounded 239.005736138 cal displays as 1,000 J after rounding; its exact supplied-input value is 1000.000000001392 J. For a stated thermochemical kilocalorie quantity choose Kilocalorie (kcal): 100 kcal is 418,400 J or 418.4 kJ, and 2,000 kcal is 8,368,000 J or 8,368 kJ.
What else is shown beside the calorie figure?: The other common energy units appear for the amount you typed, with the electronvolt available through Show 1 more. Calories and kilocalories use the thermochemical convention, and BTU uses the International Table convention. For 1,000 J that is 1 kJ, 239.005736138 cal, 0.239005736138 kcal, 0.277777777778 Wh, 0.000277777777778 kWh and 0.947817120313 BTU. Two of those are handy checks on the calorie figure: 1 Wh is 3,600 J and 860.420650096 cal, and 1 IT BTU is exactly 1,055.05585262 J and displays as 252.164400722 thermochemical cal. The electronvolt is hidden until you turn on Show 1 more in the readout, and can be chosen as a target.
Why does the page open on joules and calories when I last converted something else?: This focused page opens on Joule and Calorie, while preserving the main converter’s saved unit pair. When storage is usable, a saved value and uncommon-unit preference can travel between pages. Its suffix must still match From. Valid deliberate scalar edits can save those fields after a short delay; invalid or incomplete drafts preserve the saved record. Unusable or conflicting records remain until you use Forget saved settings, which keeps the current conversion on screen. Your input and converted values are calculated in the browser and are not uploaded by the converter. The definitions arrive with the page, so conversion needs no external data lookup and keeps working offline after the page has loaded. The core conversion needs no account.

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.