The Astronomical Unit Calculator converts distances between astronomical units (AU) and other length units — kilometers, miles, light-years, and parsecs. One AU equals exactly 149,597,870.7 km — the mean Earth-Sun distance — the foundational unit of the solar system distance scale.
149,597,871
km
92,955,807
mi
8.32
min
149,597,871
km
92,955,807
mi
8.32
min
The distance from Earth to the Sun is the ruler with which astronomers first measured the solar system. One astronomical unit (AU) — 149,597,870.7 km exactly — is that ruler, and the calculator for astronomical units converts between AU and all other astronomical and everyday length units, letting you translate the abstract distances of planetary orbits into concrete comparisons.
Since 2012, the AU has been fixed by IAU definition as exactly 149,597,870,700 meters (approximately 149.6 million km or 93.0 million miles). Key conversion factors:
Use this online calculator for any AU conversion. The light-year conversion calculator handles the complementary astronomical distance unit.
The AU makes planetary distances immediately intuitive:
Before space probes, the AU was measured using the parallax of Mars and Venus transits. Edmond Halley in 1716 proposed using transits of Venus across the Sun disk: observers at widely separated locations on Earth would see Venus cross the solar disk at slightly different times due to parallax, enabling triangulation of the AU to within 2% accuracy. The 1769 transit (observed by Captain Cook's expedition, among others) yielded AU = 153 million km — within 2.3% of the modern value. Radar ranging of Venus, first achieved in 1961, reduced the uncertainty to parts per billion. The parsec to light-year calculator and specialized length converters cover related astronomical distance units.
Kepler's third law states that the square of a planet's orbital period (in Earth years) equals the cube of its semi-major axis (in AU): T² = a³. This elegant relationship requires no knowledge of absolute distances — only relative distances in AU. Jupiter at 5.2 AU: T² = 5.2³ = 140.6; T = 11.86 years. Neptune at 30.1 AU: T² = 30.1³ = 27,271; T = 165.1 years. The AU is therefore not just a unit of convenience — it is the natural scale unit that makes Kepler's law numerically simple.
1 AU = 149,597,870.7 km (IAU 2012 definition). Light travels 1 AU in about 8.317 minutes.
The results use exact international conversion factors. Compare values against standard reference tables to verify accuracy. Use the appropriate unit for your field — metric for international standards, imperial for US/UK applications.
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Default value conversion.
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Scaled-up conversion.
An AU is the average distance from Earth to the Sun: 149,597,870.7 km (about 93 million miles).
Mars orbits at about 1.52 AU from the Sun (227.9 million km).
Light takes approximately 8 minutes and 19 seconds to travel 1 AU.
AU provides a convenient scale for measuring distances within our solar system, making large numbers more manageable.
Neptune orbits at about 30.07 AU from the Sun (4.5 billion km).
All conversions use exact international definitions, providing results accurate to floating-point precision (about 15 significant digits).
Yes, simply use the inverse formula or look for the reverse converter in our collection.
This conversion is commonly used in science, engineering, education, and professional applications requiring precise measurements.
This conversion uses internationally defined exact factors wherever possible. Any approximation is noted in the results.
Conversion factors are from NIST, BIPM (International Bureau of Weights and Measures), and ISO standards.
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