Escape Velocity Calculator

Escape speed for planets and the Moon from NASA mass data.

What it does

Escape velocity is the speed that spends every drop of kinetic energy climbing out of a gravity well: launch slower and fall back, faster and leave forever. Earth demands 11.2 km/s while the Moon asks 2.4 and Jupiter 59.5.

The tool above takes a planet or the Moon. It returns escape speed in km/s with mph and circular orbit speed beside it. The default Earth gives 11.2 km/s (25,004 mph) with orbit at 7.9 km/s.

Forms match OpenStax with NASA fact sheets behind them: total energy zero at infinity gives v as root(2GM/R) for any mass m, which cancels out. Worked checks agree, from Earth at 1.12e4 m/s to NASA anchors for the Moon, Mars, and the giants.

No atmosphere enters the math. Real rockets fight drag and steer, and rotation donates near 460 m/s at the equator, which is why launch sites hug low latitudes.

How to use

1. Pick a planet or the Moon.
2. Read escape km/s first, mph beside it.
3. Read orbit speed for satellite context.
4. Compare bodies by radius and mass, not looks.
5. Add rotation help only outside this page.
6. Ignore direction: energy is scalar.

Formula

G

Gravitational constant 6.67430e-11 SI.

M, R

Body mass and radius from NASA figures.

orbit

Circular speed at the surface radius.

Mass uses NASA rounded figures, so borderline bodies can sit 0.1 off NASA rounded columns (Mercury 4.2 here versus 4.3 printed). Direction never matters to the energy ledger.

Worked example

Reference table

Limits

• Vacuum math; atmospheres add drag.
• Surface start; altitude lowers the bar.
• Point mass model; terrain ignored.
• Rounded NASA inputs move borderline tenths.

Common mistakes

• Using diameter as radius, halving speed wrongly.
• Adding mph and km/s unconverted.
• Expecting heavy craft to need more speed.
• Forgetting orbit is slower than escape.
• Launching west against rotation.

Try it yourself

Quick checks. Answers sit tucked under each question.

Questions

Sources

• NASA NSSDC: Planetary Fact Sheet
• OpenStax University Physics: Gravitational Potential Energy

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