Astronomy calculators
6 free tools
Playful, quick calculators for the questions space makes you ask. See how much you'd weigh on Mars, how many birthdays you'd have on Jupiter, how long light takes to reach you, and the physics behind escape velocity, telescopes, and gravity.
Find out how old you'd be on each planet, based on how long it takes to orbit the Sun.
Find the speed needed to break free of a body's gravity from its mass and radius.
Find the gravitational pull between any two masses using Newton's law of gravitation.
Enter a distance and find out how long light takes to cross it at 299,792 km per second.
Work out a telescope's magnification, max useful power, and exit pupil from its focal lengths and aperture.
See what you'd weigh on every planet, the Moon, and Pluto, based on each world's surface gravity.
Frequently asked questions
Are these astronomy calculators accurate?
They use published surface-gravity ratios, orbital periods, and standard physics constants like the speed of light and the gravitational constant. Values are rounded for readability but line up with textbook figures.
Why does my weight change from planet to planet?
Your mass stays the same everywhere. Weight is mass times the local pull of gravity, and each world's gravity is different — the Moon pulls about a sixth as hard as Earth, while Jupiter pulls more than twice as hard.
Do I need to know any physics to use these?
No. Type in a weight, an age, or a distance and read the answer. The tools that use formulas — escape velocity, gravity, telescope power — come with presets and plain-language explanations.