E = mc² Calculator (Mass–Energy Equivalence)
Enter a mass to see its energy equivalent.
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Energy (J)
Energy (J)
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In kilowatt-hours
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In tons of TNT
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Mass (kg)
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E = mc² Calculator (Mass–Energy Equivalence) by TheCalcTools
How the E = mc² Calculator (Mass–Energy Equivalence) works
Einstein’s special relativity shows that mass and energy are equivalent: E = mc², with c = 299,792,458 m/s exactly. Because c² is so large, a tiny mass corresponds to a huge energy.
Nuclear reactions convert well under 1% of their fuel’s mass into energy; matter–antimatter annihilation would convert all of it. One ton of TNT is defined as 4.184 × 10⁹ J.
The formula
E = m c²
Worked example
Using the default values shown in the calculator:
| Convert | Mass to energy |
|---|---|
| Mass (kg) | 0.001 |
| Energy (J) | 1e+14 |
- 1 gram converts to 89875500000000 J, or 24,965,422 kWh, about 21,480.8 tons of TNT.
Result:
| Energy (J) | 89875500000000 |
|---|---|
| In kilowatt-hours | 24,965,422 |
| In tons of TNT | 21,480.8 |
| Mass (kg) | 0.001 |
Frequently asked questions
How much energy is in 1 gram of matter?
About 9 × 10¹³ J, roughly 25 million kWh or 21 kilotons of TNT.
Sources and further reading
- Wikipedia: Mass–energy equivalence
- NIST CODATA: Fundamental physical constants
- Wikipedia: TNT equivalent
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.