Calculate total, rest and kinetic energy of a particle at relativistic speed.
The Lorentz factor grows without bound as speed approaches c, so kinetic energy diverges — which is why massive particles cannot reach light speed. At 0.9c the classical formula understates kinetic energy by more than a factor of two. Particle accelerators are rated in energy rather than speed precisely because speed saturates near c while energy keeps rising.
Relativistic Energy
E = γ m₀ c², with γ = 1 ÷ √(1 − v²/c²)
E = γ m₀ c², with γ = 1 ÷ √(1 − v²/c²) The Lorentz factor grows without bound as speed approaches c, so kinetic energy diverges — which is why massive particles cannot reach light speed. At 0.9c the classical formula understates kinetic energy by more than a factor of two.
Particle accelerators are rated in energy rather than speed precisely because speed saturates near c while energy keeps rising.
This calculator takes 2 inputs: Rest mass, Speed as a fraction of light speed. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.