Zettajoule is 1e+21 joule units.
Zettajoules to Kilocalories Converter — ZJ to kcal
Convert Zettajoule (ZJ) to Kilocalorie (kcal) using the exact conversion factor (1 zettajoule = 2.390057e+17 kilocalorie). See the formula, worked examples, and conversion table.
Zettajoules to Kilocalories 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 kilocalorie is 1,000 calories.
Result = input x 1e+21 / 4184.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Zettajoules to Kilocalories
Zettajoule and Kilocalorie both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Specifically: Zettajoule is 1e+21 joule units, and a kilocalorie is 1,000 calories.
Formula
kilocalories = zettajoules × 2.390057e+17
This factor comes from each unit's defined relationship to the category's base unit: 1 zettajoule equals 1e+21 base units, and 1 kilocalorie equals 4184 base units, so dividing one by the other gives the direct zettajoule-to-kilocalorie factor of 2.390057e+17.
Simple example
1 ZJ × 2.390057e+17 = 2.390057e+17 kcal
1 zettajoule = 2.390057e+17 kilocalories.
Real-world example
100 ZJ × 2.390057e+17 = 2.390057e+19 kcal
100 zettajoules = 2.390057e+19 kilocalories.
Conversion table
| Zettajoule (ZJ) | Kilocalorie (kcal) |
|---|---|
| 1 ZJ | 2.390057e+17 kcal |
| 10 ZJ | 2.390057e+18 kcal |
| 100 ZJ | 2.390057e+19 kcal |
| 500 ZJ | 1.195029e+20 kcal |
| 1,000 ZJ | 2.390057e+20 kcal |
| 2,000 ZJ | 4.780115e+20 kcal |
Reverse conversion: Kilocalorie to Zettajoule
2.390057e+17 kcal × 4.184e-18 = 0.9999998488 ZJ
2.390057e+17 kilocalories = 0.9999998488 zettajoules.
zettajoules = kilocalories × 4.184e-18
For a page dedicated to this direction, see Kilocalorie to Zettajoule.
Understanding the Zettajoule (ZJ)
Zettajoule is 1e+21 joule units.
Understanding the Kilocalorie (kcal)
A kilocalorie is 1,000 calories.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilocalories are in 1 zettajoule?
1 zettajoule equals 2.390057e+17 kilocalories, using the exact defined conversion factor rather than an estimate.
How do I convert zettajoule to kilocalorie?
Multiply the zettajoule value by 2.390057e+17. The converter above does this instantly to whatever precision you set.
How do I convert kilocalorie back to zettajoule?
Use the reverse factor: 1 kilocalorie equals 4.184e-18 zettajoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a zettajoule?
Zettajoule (ZJ) is a unit of energy.
What is a kilocalorie?
Kilocalorie (kcal) is a unit of energy.
Is the zettajoule to kilocalorie conversion exact?
Yes. Both zettajoule and kilocalorie are defined by fixed standards rather than physical artifacts, so the factor of 2.390057e+17 used above is exact to as many digits as you choose to display.