Mass-Energy Equivalence Calculator: E = mc² Calc...

Einstein's Mass-Energy Equivalence

E = mc² is Einstein's famous equation from special relativity (1905), stating that mass and energy are interchangeable. A tiny mass contains enormous energy: 1 gram of any matter is equivalent to ~9×10¹³ J — enough to power a city for weeks. This underlies nuclear fission, fusion, and particle physics.

💫 E = mc² Calculator

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📐 Formula

E = m × c²

m = mass (kg), c = speed of light = 2.998×10⁸ m/s, c² = 8.988×10¹⁶ J/kg. Energy in Joules. Also: E = mc² in eV for particle physics.

📝 Worked Example

Energy in 1 gram (0.001 kg) of matter:
E = 0.001 × (3×10⁸)² = 0.001 × 9×10¹⁶ = 9×10¹³ J = 90 terajoules
Equivalent to ~21.5 kilotons of TNT (Hiroshima bomb ≈ 15 kt)

📝 How to Use

Enter MassInput mass in kg, grams, or atomic mass units (u).

Calculate EnergyView energy in Joules, MeV, kWh, and TNT equivalent.

Nuclear Reaction ModeEnter mass before and after reaction — get the mass defect energy released.

CompareSee how different masses compare in energy content.

❓ FAQ

Why is nuclear energy so powerful?

Even tiny mass defects in fission/fusion yield enormous energy. Uranium-235 fission: mass defect ~0.1% of mass, but c² amplifies it enormously.

What is matter-antimatter annihilation?

When matter meets antimatter, all mass converts to energy (100% efficiency). 1g of matter + 1g antimatter → 1.8×10¹⁴ J. Current accelerators cannot produce significant amounts.