How this calculator works
Rest mass corresponds to rest energy mc². Multiplying a mass change by c² gives its energy equivalent; dividing energy by c² gives the corresponding mass. The light speed used is exactly 299792458 m/s. This relation does not say that an ordinary process can convert an entire object into useful energy. Binding-energy differences, conversion mechanisms and efficiency determine an actual released amount. A moving object also has kinetic energy in addition to rest energy.
Formula
E0 = mc²; m = E0/c²; c² = 89875517873681764 m²/s².
Worked example
A rest mass of 1 kg corresponds to 8.9875517873681764e16 J. Twice that energy has mass equivalent 2 kg.
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Frequently asked questions
Is this kinetic energy?
It is rest energy. Relativistic kinetic energy is (gamma-1)mc².
Can all of this become usable power?
The equation gives an energy equivalent. A physical conversion process and its efficiency determine usable energy and power.
Can I enter a mass defect?
Yes. Enter the positive mass difference to find the equivalent energy released.