Mass-Energy Equivalence Calculator
Convert any mass into its equivalent rest energy using Einstein’s E = m·c².
How it works
- 1Enter the mass in kilograms (metric) or pounds (imperial) — the toggle switches unit systems.
- 2The calculator converts your input to kg and applies E = m·c², where c = 299,792,458 m/s.
- 3Results appear in joules, kilowatt-hours, and kilotons of TNT to convey the enormous scale.
Use cases
- Physics students exploring special relativity and mass–energy equivalence.
- Science communicators illustrating how much energy is locked inside ordinary matter.
- Researchers estimating theoretical energy yields in nuclear or particle physics.
Frequently asked questions
What is the formula used?
Einstein’s mass–energy equivalence: E = m·c², where m is mass in kilograms and c is the speed of light (≈ 3×10⁸ m/s). The result E is in joules.
How much energy is in a tiny mass?
The amounts are staggering. Just 1 gram (0.001 kg) converts to E = 0.001 × (3×10⁸)² ≈ 9×10¹³ J — roughly 21.5 kilotons of TNT. This is why nuclear reactions, which convert only a tiny fraction of mass, release so much energy.
Does this apply to everyday objects?
Yes — every object has rest energy m·c². But extracting it requires matter–antimatter annihilation or similar exotic processes. Chemical reactions convert only about one part in ten billion of the mass-energy, which is why E = m·c² matters for nuclear physics, not burning a log.
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