E=mc² converter
Convert mass into the energy it is worth, and back. A kilogram is 89.9 petajoules, or 21.5 megatonnes of TNT.
That's 1,000× as much as a paperclip, while a person is 70× more. That energy would run about 7,133,000 homes for a year.
What it means
How much energy is that?
This is the full rest energy. No process releases all of it: fission converts about 0.1% of the fuel’s mass, and chemical burning around a billionth.
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Three things worth knowing
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1 u = 931.5 MeV
The workhorse conversion of nuclear physics. Binding energies are just mass differences read through c².
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The missing mass
A helium nucleus weighs less than the particles that make it. The difference, converted by c², is the energy released when they joined — which is what powers the Sun.
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Nothing converts all of it
A kilogram of uranium is worth 21.5 megatonnes of TNT on paper, but fission releases about 0.1% of that. Only matter meeting antimatter converts the lot.
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Background
About E=mc²
Einstein’s equation is a conversion factor: mass and energy are the same thing measured in different units, and c² is the exchange rate. One kilogram is 8.99 × 10¹⁶ joules.
It is also why the atomic mass unit and the megaelectron volt are interchangeable in nuclear physics: 1 u is 931.5 MeV.