🕳️ Black Hole Collision Calculator
Enter the masses of two merging black holes to estimate the final remnant mass and the energy radiated as gravitational waves.
What happens when black holes collide?
When two black holes spiral together and merge, they don’t simply add their masses. A portion of their combined mass-energy is radiated away as gravitational waves, ripples in spacetime detected by observatories like LIGO and Virgo.
The formula
This calculator uses a widely cited approximation from numerical relativity: the radiated energy fraction scales with the symmetric mass ratio η = (m1 × m2) ÷ (m1 + m2)2, roughly as Eradiated ÷ M ≈ 0.2η. For two equal-mass black holes (η = 0.25), this gives about 5% of the total mass radiated away, consistent with the historic GW150914 detection.
This is a simplified fitting approximation; the true radiated fraction also depends on spin, orbital eccentricity, and mass ratio in more detailed ways captured only by full numerical relativity simulations. Use this for general astrophysics education, not research-grade prediction.