Orbital mechanics, escape velocity, stellar luminosity, and planetary calculators. Browse our free astronomy tools below — all calculators are instant, accurate, and require no sign-up.
Alien Civilization Calculator — Classify civilizations on the Kardashev scale, estimate energy budgets, project growth timelines, and explore Dyson sphere parameters.
Drake Equation Calculator — Estimate the number of communicating civilizations in the Milky Way using all seven Drake Equation factors with preset scenarios.
Earth Orbit Calculator — Calculate orbital distances, velocities, perihelion, aphelion, and seasonal solar declination for Earth or any planet.
Exoplanet Calculator — Characterize exoplanets — compute gravity, density, equilibrium temperature, habitability, and compare with known worlds.
Gravitational Time Dilation Calculator — Calculate how gravity warps time using general relativity — compare clocks near massive objects, black holes, neutron stars, and Earth.
Exoplanet Travel Planner Calculator — Plan interstellar journeys — calculate travel times, time dilation effects, energy requirements, and compare speeds for exoplanet destinations.
Hubble's Law Calculator — Calculate recession velocity, distance, and redshift using Hubble's Law. Compare Hubble constant values and explore the expanding universe.
Kepler's Third Law Calculator — Calculate orbital periods, distances, and central masses using Kepler's Third Law with solar system verification and unit conversions.
Length Contraction Calculator — Calculate relativistic length contraction at any fraction of the speed of light with visual comparisons, Lorentz factor tables, and speed references.
Light-Year Calculator — Convert between light-years, parsecs, AU, and km. Calculate light travel times and compare cosmic distances to known objects.
Luminosity Calculator — Calculate stellar luminosity from radius and temperature using the Stefan-Boltzmann law. Includes spectral classification and habitable zone estimates.
Orbital Period Calculator — Calculate the orbital period for any body orbiting a central mass. Includes solar system verification, unit conversions, and binary system mode.
Schwarzschild Radius Calculator — Calculate the event horizon radius of a black hole from its mass. Includes photon sphere, ISCO, Hawking temperature, and famous black hole comparisons.
Time Dilation Calculator — Calculate special relativistic time dilation from velocity. Find the Lorentz factor, dilated time, and compare effects at various speeds from walking to near-light.
Weight on Other Planets Calculator — Calculate your weight on every planet, moon, and dwarf planet in the solar system. Includes gravity comparison chart, jump height estimates, and planetary data.