Gravity & Space Calculators: Free Fall, Orbits and Rockets

These gravity and space calculators help you solve problems involving gravitational attraction, motion under gravity, and spaceflight. Use the Free Fall Calculator to find how fast and how far an object falls, or the Gravitational Force Calculator to apply Newton's law of universal gravitation between any two masses. The Weight on Planets Calculator shows how your weight changes across the solar system. For spaceflight questions, the Escape Velocity Calculator and Orbital Velocity Calculator determine the speeds needed to leave or circle a planet, while the Rocket Equation Calculator (Tsiolkovsky equation) estimates the delta-v a rocket can achieve. Ideal for physics students, teachers, engineers, and space enthusiasts.

Schwarzschild Radius

Enter any mass in kg, tonnes, Earth masses or Solar masses to find its Schwarzschild radius — the event-horizon size the object would have as a black hole, with interpretation of the result.

Weight on Planets

Enter your mass or Earth weight and instantly see what you would weigh on the Moon, Mars, Jupiter, the Sun, Pluto and every other planet in the Solar System.

Free Fall

Calculate free fall time, impact velocity, and distance fallen from height, time, or final speed. Enter any one known quantity, initial velocity, and gravity to get instant results.

Orbital Velocity

Calculate the speed needed for a circular orbit around Earth, the Moon, Mars, Jupiter, the Sun, or a custom body. Enter an altitude or orbital radius and get the orbital velocity, period, and orbit length.

Gravitational Force

Calculate the gravitational attraction force between two masses using Newton's law of universal gravitation. Enter the two masses, the distance between their centres, and get the force in newtons, pound-force and more.

Rocket Equation

Calculate the ideal delta-v of a rocket from the Tsiolkovsky rocket equation. Enter the exhaust velocity (or specific impulse), the initial wet mass and the final dry mass.

Escape Velocity

Calculate the escape velocity of Earth, the Moon, Mars, the Sun or any custom body from its mass and radius, using vₑ = √(2GM/R). Results in km/s, m/s, mph and more, plus surface gravity.

Hohmann Transfer

Compute the two burns, total delta-v and transfer time of a Hohmann transfer between two coplanar circular orbits. Enter the gravitational parameter and the two orbit radii.