Kilometres
0
Equivalent distance
Accurate conversion between Astronomical Units (AU) and Kilometres (km)
Convert Astronomical Units to Kilometres instantly with precise calculations. Includes reverse km to AU conversion, full formula reference, solar system distance examples, and AU conversion tables for 2026.
Professional distance conversion for astronomy, space science, navigation, and education
Convert Astronomical Units (AU) to Kilometres using the exact IAU-defined value: 1 AU = 149,597,870.7 km. One Astronomical Unit is defined as the mean distance between the Earth and the Sun — approximately 149.6 million kilometres. Our tool delivers full-precision results for any AU value you enter, from tiny fractions to thousands of AU.
Switch between AU to km and km to AU conversion instantly. Whether you are calculating the distance of a planet from the Sun in kilometres, converting a spacecraft trajectory, or converting a published km figure back to AU for easy comparison, both directions are handled from a single input field.
Essential for astronomy students, educators, space science researchers, and enthusiasts in 2026. AU-to-km conversions are used when working with planetary distances, asteroid orbits, telescope targeting, mission planning, and comparing solar system scales. The result breakdown also shows metres and miles for complete reference.
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An Astronomical Unit (AU) is the standard unit of measurement used in astronomy to describe distances within our solar system. It is defined by the International Astronomical Union (IAU) as exactly 149,597,870,700 metres — or approximately 149.6 million kilometres. This value is based on the mean distance between the Earth and the Sun, averaged over one orbital year.
The symbol au is the modern IAU-recommended notation, though AU and a.u. are also widely used. Because interplanetary distances are so vast, expressing them in kilometres produces unwieldy numbers — for example, Jupiter orbits the Sun at about 778,500,000 km. In AU, the same distance is simply 5.2 AU, making the scale far easier to understand and compare. You can explore more astronomy converters on our ConcreticMetric converter hub.
The conversion between AU and kilometres uses a single fixed constant defined by the IAU in 2012. Because the value is an exact definition (not a measured average), the conversion is perfectly precise at full significant figures.
Example: 3 AU = 3 × 149,597,870.7 = 448,793,612.1 km
Example: 299,195,741.4 km = 299,195,741.4 ÷ 149,597,870.7 = 2 AU
All planet distances are average (mean) orbital distances from the Sun
The reference table below covers the most commonly needed AU to km conversions, from small fractions up to 1,000 AU — spanning inner solar system objects to the outer reaches of the heliosphere.
| Astronomical Units (AU) | Kilometres (km) | Scientific Notation | Approximate Reference |
|---|---|---|---|
| 0.01 AU | 1,495,978.7 km | 1.496 × 10⁶ km | ~4× Earth–Moon distance |
| 0.1 AU | 14,959,787.1 km | 1.496 × 10⁷ km | ~39× Earth–Moon distance |
| 0.39 AU | 58,343,169.6 km | 5.834 × 10⁷ km | Mercury's avg. orbital distance |
| 0.72 AU | 107,710,468.1 km | 1.077 × 10⁸ km | Venus's avg. orbital distance |
| 1 AU | 149,597,870.7 km | 1.496 × 10⁸ km | Earth–Sun mean distance |
| 1.52 AU | 227,388,963.5 km | 2.274 × 10⁸ km | Mars's avg. orbital distance |
| 2 AU | 299,195,741.4 km | 2.992 × 10⁸ km | Inner asteroid belt |
| 3 AU | 448,793,612.1 km | 4.488 × 10⁸ km | Outer asteroid belt |
| 5.2 AU | 777,908,927.6 km | 7.779 × 10⁸ km | Jupiter's avg. orbital distance |
| 9.58 AU | 1,433,147,721.7 km | 1.433 × 10⁹ km | Saturn's avg. orbital distance |
| 10 AU | 1,495,978,707 km | 1.496 × 10⁹ km | Beyond Saturn |
| 19.2 AU | 2,872,278,734.4 km | 2.872 × 10⁹ km | Uranus's avg. orbital distance |
| 30.07 AU | 4,498,829,095.5 km | 4.499 × 10⁹ km | Neptune's avg. orbital distance |
| 50 AU | 7,479,893,535 km | 7.480 × 10⁹ km | Kuiper Belt outer edge |
| 100 AU | 14,959,787,070 km | 1.496 × 10¹⁰ km | Heliosphere boundary region |
| 1000 AU | 149,597,870,700 km | 1.496 × 10¹¹ km | Inner Oort Cloud |
Converting AU to km is straightforward using the IAU-defined constant. Follow these steps for accurate results every time:
In 2012, the International Astronomical Union redefined the AU as an exact fixed constant: 149,597,870,700 metres. Before this, the AU was based on a measured value with slight uncertainty depending on gravitational models and solar mass estimates.
The AU was originally conceived as the average (mean) distance between the Earth and the Sun. Earth's orbit is elliptical, ranging from 147.1 million km (perihelion, closest) to 152.1 million km (aphelion, farthest) — the AU sits right at the average of these two extremes.
Light travels 1 AU in approximately 8 minutes and 20 seconds. This means sunlight takes about 8.3 minutes to reach Earth. At Neptune (30.07 AU), sunlight takes roughly 4 hours 10 minutes to arrive — a useful way to appreciate solar system scale.
Voyager 1, the most distant human-made object, is currently over 160 AU from the Sun — equivalent to approximately 23.9 billion kilometres. AU is the standard unit used by NASA and ESA to track deep space mission distances in real time.
Kilometres produce extremely large and unwieldy numbers for astronomical distances. For example, the distance from the Sun to Neptune is 4,498,829,095 km — hard to grasp. Expressed as 30.07 AU, it immediately conveys that Neptune is about 30 times farther from the Sun than Earth is.
For distances beyond the solar system, astronomers switch to larger units: a light-year (~63,241 AU) or a parsec (~206,265 AU). AU remains the preferred unit for anything within our solar system, including asteroid tracking, planetary orbits, and comet perihelion distances.
1 AU = 149,597,870.7 km = 149,597,870,700 m = 92,955,807.3 miles
The AU is an exact definition — there is no rounding or uncertainty in the conversion constant.
The Mars Science Laboratory (Curiosity Rover) launched when Mars was approximately 1.65 AU from Earth.
1.65 × 149,597,870.7 = 246,836,987.7 km — that's nearly 247 million kilometres of travel through space.
The AU is defined as exactly 149,597,870,700 metres (149,597,870.7 km). Some sources round this to 149,598,000 km or 1.496 × 10⁸ km for brevity. For scientific and engineering calculations, always use the full IAU constant: 149,597,870.7 km.
The International Astronomical Union officially defined the Astronomical Unit as exactly 149,597,870,700 metres in 2012 Resolution B2. This is the authoritative standard used in all scientific and engineering calculations worldwide.
Visit IAU →NASA publishes real-time and mean orbital distances for all solar system bodies in both AU and kilometres. Ideal for students, educators, and researchers working on planetary science, mission planning, or astronomy education in 2026.
Visit NASA →ConcreticMetric offers free converters for length, area, pressure, energy, time, and more. All tools are mobile-friendly, free to use, and built for accuracy in 2026 with instant results and full formula references.
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