A tiny amount of mass corresponds to an enormous amount of energy because the speed of light squared is huge.
How to use the E = mc² Calculator
- Mass
- Want to work backwards? Type a value into Energy and Mass is calculated for you.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Multiply mass in kilograms by the speed of light squared.
What each result means
- Energy = [Mass] × 299792458^2
- In kilowatt-hours = [Energy] ÷ 3.6e6
- TNT equivalent = [Energy] ÷ 4.184e12
Example values
How the main result changes when Mass changes and everything else stays at the example values above:
| Mass (g) | Energy (J) |
|---|---|
| 0.5 | 44,937,758,936,840.88 |
| 0.75 | 67,406,638,405,261.32 |
| 1 | 89,875,517,873,681.77 |
| 1.25 | 112,344,397,342,102.2 |
| 1.5 | 134,813,276,810,522.64 |
| 2 | 179,751,035,747,363.53 |
Formula
E = m c²Worked example
Inputs — Mass: 1 g.
Results — Energy = 89,875,517,873,681.77 J; In kilowatt-hours = 24,965,422 kWh; TNT equivalent = 21.481 kilotons.
Frequently asked questions
How much energy is in one gram?
About 9 × 10¹³ J, around 21 kilotons of TNT.
Does a nuclear reactor convert all its fuel to energy?
No, only a tiny fraction of the mass is converted.
What formula does the E = mc² Calculator use?
E = m c².
Can I work backwards from the result?
Yes. Type the result you want into Energy and the calculator finds the matching mass.