Astronomy & Space Calculators
Explore the sky by the numbers, find the moon phase and sunrise for any date, discover your weight and age across the solar system, work out light travel times and angular sizes, and size up a telescope. Real astronomical algorithms and NASA data, running entirely in your browser.
- Moon Phase Calculator Pick a date to see the moon phase, its name, how illuminated it is, its age in days, and when the next full and new moon fall.
- Sunrise & Sunset Calculator Enter a date and location to get the sunrise, sunset, solar noon and day length, from the NOAA solar algorithm.
- Weight on Other Planets Enter your Earth weight to see what you'd weigh on the Moon, Mars, Jupiter, the Sun and every planet.
- Age on Other Planets Calculator Enter your age or birthday to see how old you'd be on every planet, where a "year" is one trip around the Sun.
- Light Travel Time Calculator Enter a distance to see how long light takes to travel it, and the distance in km, AU, light-years and parsecs.
- Angular Size Calculator Enter an object's diameter and distance to get its angular size, how big it appears, in degrees, arcminutes and arcseconds.
- Telescope Calculator Enter your telescope's focal length, aperture and eyepiece to get magnification, focal ratio, exit pupil and resolving power.
- Parallax Distance Calculator Convert a star's parallax angle to its distance, in parsecs and light-years, or work out the parallax for a given distance.
- Golden & Blue Hour Calculator Enter a date and location to get the morning and evening golden hour and blue hour windows, plus civil, nautical and astronomical twilight.
- Star Magnitude Calculator Enter any two of apparent magnitude, absolute magnitude and distance to solve for the third, and compare how much brighter one star is than another.
- Redshift Calculator Enter a redshift or recession velocity to get the other, the stretched wavelength and a rough Hubble distance, relativistic or classical.
- Kepler's Third Law Calculator Enter a semi-major axis to get the orbital period, or a period to get the distance, for the Sun or any central mass.
- Schwarzschild Radius Calculator Enter a mass to get its Schwarzschild radius: how small it would have to be squeezed to become a black hole.
Frequently asked questions
Are these astronomy calculators accurate?
Yes. They use established astronomical constants and algorithms: the synodic month for lunar phase, the NOAA solar-position algorithm for sunrise/sunset (±1 minute), NASA planetary data for gravity and orbits, and the IAU-defined light-year and parsec. Sources are cited on each tool.
Do the sunrise and moon tools use my location?
You enter your latitude, longitude and date yourself (or pick a city), nothing is fetched or tracked. The moon phase needs only a date.
Is this real-time astronomical data?
No. These are calculators. They compute phases, times, distances and optics from the values you enter and fixed astronomical constants, not a live feed.
Is my data uploaded?
No. Every tool runs entirely in your browser, nothing is sent to a server, and they work offline.