Gigajoule is 1000000000 joule units.
Gigajoules to Calories Converter — GJ to cal
Convert Gigajoule (GJ) to Calorie (cal) using the exact conversion factor (1 gigajoule = 239,005,736.1 calorie). See the formula, worked examples, conversion table, history, and common uses.
Gigajoules to Calories converter
Converter
Energy Converter
Convert joules, calories, kilowatt-hours, BTU, electronvolts, therms, and mechanical work units.
Context values
Some unit families need one extra value for a physically accurate result.
A thermochemical calorie is 4.184 joules.
Result = input x 1e+9 / 4.184.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Gigajoules to Calories
Gigajoule and Calorie both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Specifically: Gigajoule is 1000000000 joule units, and a thermochemical calorie is 4.184 joules.
Formula
calories = gigajoules × 239005736.138
This factor comes from each unit's defined relationship to the category's base unit: 1 gigajoule equals 1000000000 base units, and 1 calorie equals 4.184 base units, so dividing one by the other gives the direct gigajoule-to-calorie factor of 239005736.138.
Simple example
1 GJ × 239005736.1 = 239,005,736.1 cal
1 gigajoule = 239,005,736.1 calories.
Real-world example
100 GJ × 239005736.1 = 23,900,573,610 cal
100 gigajoules = 23,900,573,610 calories.
Conversion table
| Gigajoule (GJ) | Calorie (cal) |
|---|---|
| 1 GJ | 239,005,736.1 cal |
| 10 GJ | 2,390,057,361 cal |
| 100 GJ | 23,900,573,610 cal |
| 500 GJ | 119,502,868,100 cal |
| 1,000 GJ | 239,005,736,100 cal |
| 2,000 GJ | 478,011,472,300 cal |
Reverse conversion: Calorie to Gigajoule
1 cal × 4.184e-9 = 4.184e-9 GJ
1 calorie = 4.184e-9 gigajoules.
gigajoules = calories × 4.184e-9
For a page dedicated to this direction, see Calorie to Gigajoule.
Understanding the Gigajoule (GJ)
Gigajoule is 1000000000 joule units.
Understanding the Calorie
Calorie (cal) measures energy. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. It is classified as a Non-SI unit (limited use with SI).
Where it's used: Nutrition labeling in the US and several other countries still commonly uses the kilocalorie (as 'Calorie')
Calorie vs. Calorie (kilocalorie). Food labels' capitalized 'Calorie' is actually one kilocalorie (1,000 small calories) — a long-standing labeling convention that causes frequent confusion.
Uses of the Calorie today
- Food energy labeling (as kilocalories, often written 'Calories')
- Historical chemistry and thermodynamics contexts
History of the Calorie
The calorie was originally defined in the early 19th century as the heat needed to raise one gram of water by one degree Celsius, but different scientific traditions defined it at slightly different reference temperatures, producing several close but non-identical 'calorie' values historically (15 °C calorie, mean calorie, thermochemical calorie).
To resolve this ambiguity, the thermochemical calorie was fixed by convention at exactly 4.184 joules; the very similar International Table calorie is fixed at exactly 4.1868 joules. The nutritional 'Calorie' seen on food labels is actually a kilocalorie (1,000 calories).
Historical origin. Calorie was not the invention of a single named person; it developed through the process described above.
Calorie — sources
- NIST Special Publication 811 — Documents the thermochemical calorie's exact joule equivalence.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many calories are in 1 gigajoule?
1 gigajoule equals 239,005,736.1 calories, using the exact defined conversion factor rather than an estimate.
How do I convert gigajoule to calorie?
Multiply the gigajoule value by 239005736.1. The converter above does this instantly to whatever precision you set.
How do I convert calorie back to gigajoule?
Use the reverse factor: 1 calorie equals 4.184e-9 gigajoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a gigajoule?
Gigajoule (GJ) is a unit of energy.
What is a calorie?
Calorie (cal) measures energy. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. It is classified as a Non-SI unit (limited use with SI).
Is the gigajoule to calorie conversion exact?
Yes. The thermochemical calorie used in this converter is defined as exactly 4.184 joules. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between calorie vs. calorie (kilocalorie)?
Food labels' capitalized 'Calorie' is actually one kilocalorie (1,000 small calories) — a long-standing labeling convention that causes frequent confusion.