Astronomy Calculators
Sunrise and Sunset Calculator
Sunrise and sunset times, solar noon, day length and civil twilight for a city or coordinates on any date.
Kepler's Third Law Calculator
Orbital period from the semi-major axis and back, comparing orbits, and satellite periods by Kepler's third law.
Moon Phase Calculator
The Moon phase and illumination on any date, the Moon's age and the exact times of new and full moons in your time zone.
Astronomical Units Converter: AU, Light-Year, Parsec
Convert kilometers, astronomical units, light-years and parsecs, with a solution and the light travel time.
Age on Other Planets Calculator
How old you are on Mercury, Venus, Mars, Jupiter and other planets and when your next birthday on each of them will be.
Telescope Calculator: Magnification, Resolution and Newtonian
Magnification, exit pupil, field of view, resolution, limiting magnitude and the Newtonian diagonal.
Sky Position Calculator: Altitude, Azimuth and Visibility
The altitude and azimuth of an object, culminations and visibility over the year from its coordinates and your location.
Angular Distance on the Celestial Sphere Calculator
The angular distance between two points on the celestial sphere from their coordinates.
Celestial Coordinate Converter: Equatorial, Ecliptic, Galactic
Convert between equatorial, ecliptic and galactic coordinates for epoch J2000.
Astrophotometry Calculator: Magnitude and Brightness
Magnitude, brightness ratio, absolute magnitude and distance.
Atmospheric Refraction Calculator: True and Apparent Altitude
Refraction and the conversion of true altitude to apparent and back, with pressure and temperature.
Sidereal Time Calculator: Local Sidereal Time
Local sidereal time from the date, universal time and longitude.
Noon Sun Height Calculator
The Sun's height above the horizon at noon at any latitude on equinoxes, solstices or any date; latitude from the Sun's height.
Weight on Other Planets Calculator
How much you would weigh on the Moon, Mars, Jupiter and other planets: weight P = m · g and scale readings for all Solar System bodies.
Day Length Calculator
Length of daylight, sunrise and sunset in local solar time for any latitude and date, polar day and polar night.
Gravitational Force Calculator (Newton's Law of Gravitation)
Gravitational force F = Gm₁m₂/r², distance, mass and the surface gravity of a planet.
Planets of the Solar System
The planets of the Solar System: diameter, mass, distance from the Sun, orbital period.
Brightest Stars Table
The brightest stars of the night sky: constellation, apparent magnitude and distance.
Astronomy calculators solve school problems and answer questions about the sky: how old you are on Mars, what the Moon phase is today, when the Sun rises, how a planet's orbital period depends on its orbit.
- Age on other planets — from the date of birth, with your next birthday on each planet.
- Moon phase — on any date, with the times of new and full moons.
- Sunrise and sunset — for cities and coordinates, with day length and twilight.
- Kepler's third law — periods and orbits of planets and satellites.
- Astronomical units — AU, light-years, parsecs and light time.
How much you would weigh on the Moon and other planets is calculated by the weight on other planets calculator.