Einstein showed in 1905 that mass and energy are interchangeable. One gram of matter corresponds to 9 × 10¹³ J, about the electricity a typical household uses in thousands of years. Nuclear power converts only about 0.1% of the fuel’s mass into energy.
How to use the E = mc² Calculator
- Mass m
- Every result field is editable: type into Energy E and Mass m plus every other field update to match.
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter a mass, or type an energy into the result to find the equivalent mass.
What each result means
- Energy E = [Mass m]×299792458^2
- Typical household electricity use covered = [Energy E]÷3.6e6÷10500
Example values
How the main result changes when Mass m changes and everything else stays at the example values above:
| Mass m (g) | Energy E (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·c²
Worked example
Inputs: Mass m: 1 g.
Results: Energy E = 89,875,517,873,681.77 J; Typical household electricity use covered = 2,377.6592 years.
Key terms
- Rest energy
- mc², the energy of a body at rest.
Frequently asked questions
Does mass really turn into energy?
Binding energy changes show up as tiny mass differences.
How much energy is in 1 kg?
About 9 × 10¹⁶ J (25 TWh).
Why isn't all mass converted in reactors?
Fission releases only the binding-energy difference, ~0.1%.
What converts mass completely?
Matter–antimatter annihilation.