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
- Sunrise & Sunset Calculator Enter a date and location to get the sunrise, sunset, solar noon and day length
- Weight on Other Planets Calculator 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 & Distance Calculator Enter a distance to see how long light takes to travel it
- Angular Size Calculator Enter an object's diameter and distance to get its angular size
- Telescope Calculator Enter your telescope's focal length, aperture and eyepiece to get magnification, focal ratio, exit pupil and resolving power.
- Stellar Parallax Distance Calculator Convert a star's parallax angle to its distance
- Golden Hour & 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 & Distance Calculator Enter any two of apparent magnitude, absolute magnitude and distance to solve for the third
- Redshift Calculator Enter a redshift or recession velocity to get the other, the stretched wavelength and a rough Hubble distance
- Kepler's Third Law Calculator Enter a semi-major axis to get the orbital period
- 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.