Escape Velocity Calculator
How fast must you go to leave a planet’s gravity for good?
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Escape Velocity Calculator by TheCalcTools
How the Escape Velocity Calculator works
Enter the body’s mass in kilograms and its radius in kilometres.
Escape velocity is the speed at which kinetic energy equals the gravitational binding energy.
It is √2 times the circular orbit speed.
The formula
Worked example
Using the default values shown in the calculator:
| Mass (kg) | 5.972e+24 |
|---|---|
| Radius (km) | 6371 |
- For Earth: √(2 × 6.6743 × 10⁻¹¹ × 5.972 × 10²⁴ ÷ 6.371 × 10⁶) = 11.186 km/s.
- Surface gravity is 9.820 m/s².
Result:
| Escape velocity (km/s) | 11.186 |
|---|---|
| Circular orbit speed at the surface (km/s) | 7.910 |
| Surface gravity (m/s²) | 9.820 |
Frequently asked questions
Does the escape velocity depend on the mass of the rocket?
No, only on the planet’s mass and the distance from its centre. A heavier rocket needs more energy but not a higher speed.
Why do rockets not need 11.2 km/s at launch?
They keep thrusting, so they do not have to reach escape speed instantly. The figure applies to a ballistic launch.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.