Equivalent distance
Your value in astronomical units, gigameters, and kilometers.
Home / Astronomy / Astronomical Unit
Astronomical
Astronomical Unit Calculator
Convert astronomical units (AU), the average Earth–Sun distance, to kilometers, miles, light years, and meters, with a full equivalents table.
Result
149,597,871 km
How it works
The astronomical unit is a convenient yardstick for the Solar System, defined as exactly 149,597,870.7 km. Larger interstellar distances use light years or parsecs. All relate to the meter, so conversion is a matter of scaling.
1 AU = 149,597,870.7 km
1 light year ≈ 63,241 AU · 1 parsec ≈ 206,265 AU
1 light year ≈ 63,241 AU · 1 parsec ≈ 206,265 AU
Worked example
Neptune orbits at about 30 AU, which is 30 × 149,597,871 ≈ 4.49 billion km from the Sun.
Planet distances in astronomical units
The astronomical unit is fixed by the International Astronomical Union at exactly 149,597,870.7 km, roughly the average distance from Earth to the Sun. Light takes about 8.3 minutes to cross one AU.
| Planet (average distance from the Sun) | AU / million km |
|---|---|
| Mercury | 0.387 AU = 58 million km |
| Venus | 0.723 AU = 108 million km |
| Earth | 1 AU = 150 million km |
| Mars | 1.524 AU = 228 million km |
| Jupiter | 5.203 AU = 778 million km |
| Saturn | 9.537 AU = 1,427 million km |
| Uranus | 19.19 AU = 2,871 million km |
| Neptune | 30.07 AU = 4,498 million km |
Beyond Neptune, distances are still quoted in AU: Voyager 1, the most distant spacecraft, is more than 160 AU from the Sun, while the nearest star is about 268,000 AU away, which is why light-years take over for interstellar distances.
Astronomical unit conversion table
| 1 AU equals | Value |
|---|---|
| Kilometers | 149,597,870.7 km (exact) |
| Miles | 92,955,807 mi |
| Meters | 1.495978707 × 10¹¹ m |
| Light travel time | 499.0 seconds (8 min 19 s) |
| Light-years | 0.0000158 ly |
| Parsecs | 0.00000485 pc |
Why astronomers use the AU
Kilometers produce unwieldy numbers inside the solar system, and light-years are far too large. The AU sits in between: planet and asteroid orbits come out as small, easy-to-compare numbers. Since 2012 the International Astronomical Union has defined it as a fixed length rather than a measured Earth–Sun distance, so 1 AU never changes.
Earth is not always 1 AU from the Sun
- Perihelion (closest, early January): about 0.983 AU, or 147.1 million km.
- Aphelion (farthest, early July): about 1.017 AU, or 152.1 million km.
- The 3% difference is not what causes seasons; Earth's 23.4° axial tilt does.
Distances beyond the planets
| Object or region | Distance from the Sun |
|---|---|
| Pluto (average) | 39.5 AU |
| Kuiper Belt | about 30 to 50 AU |
| Voyager 1 (2026) | more than 165 AU |
| Inner edge of the Oort Cloud (estimated) | about 2,000 AU |
| Proxima Centauri | about 268,000 AU |
Once distances reach tens of thousands of AU, astronomers switch to light-years or parsecs. Use the light-year converter for interstellar distances, or the light travel time calculator to see how long sunlight takes to reach each planet.
Frequently asked questions
How many kilometers is one AU?
Exactly 149,597,870.7 km, about 92.96 million miles.
How many AU are in a light-year?
About 63,241 AU.
How many miles is one AU?
About 92.96 million miles (92,955,807 mi).
Is 1 AU the exact Earth–Sun distance?
It is the average distance, fixed by definition at 149,597,870.7 km. Earth's real distance swings between about 0.983 and 1.017 AU over the year.
How far is Mars from Earth in AU?
It varies from about 0.37 AU at a close opposition to about 2.67 AU when Mars is on the far side of the Sun.
Related calculators
Light Year ConversionConvert light-years to kilometers, miles, AU and parsecs.
Light Speed Distance CalculatorHow far light travels in any time, from seconds to years.
Light Travel Time CalculatorHow long light takes to cross a distance, such as from the Sun or a star.
Star Distance from Parallax CalculatorA star's distance in parsecs and light-years from its parallax.
Sidereal Day to Solar Day ConverterConvert between sidereal and solar days and times.
Solar Mass to Kilograms ConverterConvert solar masses to kilograms and back.