Astronomical Unit Calculator — AU to km, Miles, Light-years
One astronomical unit (AU) is the mean Earth–Sun distance: exactly 149,597,870,700 metres by the 2012 IAU definition. This converter converts AU to and from kilometres, miles, metres, light-minutes, light-years and parsecs.
From unit
To unit
- 1
Convert to astronomical units
1 ÷ 1 = 11 AU = 149,597,870,700 m (IAU 2012 exact definition). - 2
Convert to km
1 × 149,597,870.7 = 149,597,870.7
How does this calculator work?
1 AU = 149,597,870,700 m (exact, IAU 2012) ≈ 149.6 million km ≈ 92.96 million miles ≈ 8.317 light-minutes ≈ 1.581×10⁻⁵ light-years. Enter any distance and choose units; the calculator converts to all other units simultaneously.
Formula
How this is calculated
The astronomical unit (AU or ua) was historically defined as the mean distance between the Earth and the Sun. In 2012 the International Astronomical Union (IAU) fixed it as exactly 149,597,870,700 metres (roughly 150 million kilometres or 93 million miles) to eliminate ambiguity caused by the slight relativistic effects on orbital semi-major axes. This exact value is the basis for all conversions in this calculator.
The calculator first converts your input distance to AU using the exact IAU factor, then multiplies by the target-unit factor. Light-minutes use the exact speed of light (299,792,458 m/s); light-years use the Julian year (365.25 days); parsecs are derived as 1 pc = 3.26156 light-years. All factors are exact or NIST/IAU-recommended.
For reference: Mercury orbits at ≈ 0.387 AU, Venus at ≈ 0.723 AU, Earth at 1 AU, Mars at ≈ 1.524 AU, Jupiter at ≈ 5.2 AU, and Neptune at ≈ 30.1 AU. The nearest star system (Alpha Centauri) is about 268,000 AU (≈ 4.24 light-years or 1.30 pc).
Frequently asked questions
1 AU = 149,597,870.7 km (approximately 149.6 million kilometres). This is the exact 2012 IAU definition of the astronomical unit.
Light travels 1 AU in approximately 499 seconds, or about 8 minutes and 19 seconds. This is why sunlight reaching Earth is about 8 minutes old.
An AU is the Earth–Sun distance (≈150 million km). A light-year is the distance light travels in one year (≈63,241 AU). A parsec is the distance at which 1 AU subtends one arcsecond (≈206,265 AU or ≈3.26 light-years). AUs are used within the Solar System; light-years and parsecs are used for interstellar and intergalactic distances.
Also known as
TG we-Calculate Editorial Team. (2026). Astronomical Unit Calculator — AU to km, Miles, Light-years [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/astronomical-unit-calculator
TG we-Calculate Editorial Team. "Astronomical Unit Calculator — AU to km, Miles, Light-years." TG we-Calculate. 2026. https://we-calculate.com/calculator/astronomical-unit-calculator.
TG we-Calculate Editorial Team, "Astronomical Unit Calculator — AU to km, Miles, Light-years," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/astronomical-unit-calculator
@misc{wecalculate_astronomical_unit_calculator, title = {Astronomical Unit Calculator — AU to km, Miles, Light-years}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/astronomical-unit-calculator}}, year = {2026}, note = {TG we-Calculate} }
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