E=mc2 Calculator
Calculate mass-energy equivalence using Einstein's E=mc2.
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Enter the mass in kilograms and the calculator instantly shows the equivalent energy in joules using Einstein's equation E=mc2, where c is the speed of light (299,792,458 m/s).
- Enter mass. Type the mass in kilograms.
- Read the result. The energy in joules appears instantly.
- Share or copy. Use the buttons to save or share your result.
About the E=mc2 Calculator
Einstein's mass-energy equivalence, expressed as E=mc2, shows that mass and energy are interchangeable. A small amount of mass contains an enormous amount of energy because the speed of light squared is such a large number (approximately 9 x 10^16 m2/s2). This principle is the foundation of nuclear energy and particle physics. Even 1 kilogram of matter, if fully converted to energy, would release about 90 petajoules, roughly the energy of a 21-megaton nuclear weapon.
Frequently Asked Questions
What does E=mc2 mean?
E=mc2 means that energy (E) equals mass (m) multiplied by the speed of light (c) squared. It shows that mass and energy are two forms of the same thing.
How much energy is in 1 kg of matter?
One kilogram of matter contains approximately 8.99 x 10^16 joules of energy, equivalent to about 21.5 megatons of TNT.
Is E=mc2 used in nuclear reactors?
Yes. Nuclear reactors convert a tiny fraction of the mass of uranium or plutonium into energy. The mass lost in nuclear fission becomes the thermal energy that generates electricity.