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Astronomy Calculators

Explore free astronomy calculators for the Moon, Solar System, orbital mechanics, and deep-space distances. Calculate moon phases from the Julian Date, light-travel time, your age and weight on other planets, escape and orbital velocity, Kepler's third law, stellar magnitude, parallax, and Hubble's law — and convert astronomical units, light-years, and parsecs with transparent, verified formulas.

Browse all 14 astronomy calculators below.

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Astronomical Unit Calculator

Convert astronomical units (AU) to kilometres, miles, metres, light-minutes, and light-years using the IAU exact definition.

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Moon Phase Calculator

Calculate the Moon's phase for any date and time using a real Julian Date algorithm and the 29.53-day synodic month.

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Light Travel Time Calculator

Calculate how long light takes to travel a distance using t = d / c with the exact speed of light 299,792,458 m/s.

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Escape Velocity Calculator

Calculate the escape velocity from any planet, moon, or star using ve = √(2GM/R) with NASA body data.

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Kepler's Third Law Calculator

Apply Kepler's third law T² = (4π²/GM)a³ to find an orbital period from a semi-major axis, or the axis from a period.

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Hubble Law Calculator

Calculate galaxy recession velocities from distance using Hubble's law v = H₀d, with an adjustable Hubble constant.

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All astronomy calculators (14)

Astronomical Unit CalculatorConvert astronomical units (AU) to kilometres, miles, metres, light-minutes, and light-years using the IAU exact definition.Moon Phase CalculatorCalculate the Moon's phase for any date and time using a real Julian Date algorithm and the 29.53-day synodic month.Light Travel Time CalculatorCalculate how long light takes to travel a distance using t = d / c with the exact speed of light 299,792,458 m/s.Age on Other Planets CalculatorFind out how old you would be on Mercury, Mars, Jupiter, and every planet using each world's orbital period.Weight on Other Planets CalculatorCalculate your weight on every planet, the Sun, and the Moon using each body's real surface gravity from NASA data.Parsec ConverterConvert parsecs to light-years, kiloparsecs, megaparsecs, AU, kilometres, and miles using the exact IAU definition.Escape Velocity CalculatorCalculate the escape velocity from any planet, moon, or star using ve = √(2GM/R) with NASA body data.Orbital Period CalculatorCalculate the orbital period of a body from its semi-major axis and central mass using T = 2π√(a³/GM).Angular Size CalculatorCalculate the angular size of any celestial object from its diameter and distance using θ = 2 arctan(D/2d).Kepler's Third Law CalculatorApply Kepler's third law T² = (4π²/GM)a³ to find an orbital period from a semi-major axis, or the axis from a period.Orbital Velocity CalculatorCalculate the circular orbital velocity at any radius using v = √(GM/r), with presets for the ISS and geostationary orbit.Stellar Magnitude CalculatorCalculate stellar distances from the distance modulus m − M = 5 log10(d/10 pc), or absolute magnitude from apparent magnitude.Parallax Distance CalculatorCalculate a star's distance from its parallax angle using d(pc) = 1/p(arcsec), the relation that defines the parsec.Hubble Law CalculatorCalculate galaxy recession velocities from distance using Hubble's law v = H₀d, with an adjustable Hubble constant.

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Reviewed for accuracy · Last updated October 7, 2026

Every astronomy calculators tool uses a documented, industry-standard formula reviewed by our editorial team.

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