Astronomical Unit Calculator – Exact Value of 1 AU in KM & IAU Definition
The exact value of 1 au in km is 149,597,870.7 km (or 149,597,870,700 meters exactly). This is the official IAU definition of 1 au in km established in 2012. The exact value of 1 astronomical unit in km and miles: 149,597,870.7 km and 92,955,807 miles. The exact value of 1 au since 2012 is fixed at exactly 149,597,870,700 m by the International Astronomical Union. Use this free au calculator to convert au to km, au to ly, and other units.
Last updated: January 23, 2026
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Conversion Results
Astronomical Units
Astronomical Units
1 au
Light Years
0.00001581 ly
Parsecs
0.00000485 pc
Sun Radii
214.834521 R☉
Metric Units
Meters
149,597,870,700 m
Kilometers
149,597,870.7 km
Imperial/US Units
Miles
92,955,807.27 mi
Key Facts:
- • 1 au = 149,597,870,700 m exactly (IAU 2012 definition)
- • 1 au ≈ 149.6 million km ≈ 93 million miles
- • 1 au = 0.000015813 light years
- • 1 light year = 63,241 astronomical units
- • 1 parsec ≈ 206,264.8 astronomical units
- • Earth-Sun distance averages about 1 au
Astronomical Unit Calculator Features
Exact conversion
1 au = 149,597,870,700 m
Uses the International Astronomical Union's exact 2012 definition
Astronomical units
AU, Light Years, Parsecs, Sun Radii
Convert between AU, light years, parsecs, Sun radii, and standard units
Use cases
Planet Distances, Orbital Calculations
Ideal for measuring distances between planets and other Solar System objects
Applications
Research, Education, Space Missions
Convert distances for astronomy research, education, and space mission planning
Speed
Instant calculations
See results in all units immediately as you enter or change values
Learning
Understanding Solar System Scale
Helps visualize and understand the vast distances in our Solar System and beyond
Quick Example Result
For 1 astronomical unit:
Kilometers
149,597,870.7 km
Miles
92,955,807 mi
Exact Value of 1 AU in KM & Official IAU Definition
The exact value of 1 au in km is 149,597,870.7 kilometers (or 149,597,870,700 meters exactly). This is the official IAU definition of 1 au in km (or iau definition of 1 au in km) established in 2012. The exact value of 1 astronomical unit in km and miles (or exact value of 1 astronomical unit in kilometers): 149,597,870.7 km and 92,955,807.273 miles. The exact value of 1 au since 2012 (or 1 au exact value since 2012) is fixed at exactly 149,597,870,700 m by the International Astronomical Union. Also known as exact value of 1 au in km iau definition 2012, exact definition of 1 au in km since 2012, 1 au exact value km iau, 1 au exact value iau, or 1 au exact value iau 2012.
AU Calculator & AU to KM Conversion
An au calculator (or au calculator) converts between astronomical units and other distance units. To convert au to km (or au to km, 1 au to km, au in km): multiply AU by 149,597,870.7. Example: 9.5 au to km = 9.5 × 149,597,870.7 = 1,421,179,771.65 km. The au to km formula: km = au × 149,597,870.7. Also supports au to ly (astronomical unit to light year), au to kilometers (or au in kilometers), astronomical unit to miles, and km to au conversion. Perfect for calculating 1 au distance in km exact value and other conversions.
IAU 2012 Resolution B2 & Exact Definition
The iau 2012 resolution b2 astronomical unit 149597870700 m exact established the exact value. The exact value of 1 au in km iau 2012 (or exact value of 1 au in km iau definition) is exactly 149,597,870,700 meters. Also known as 1 au exact value km, 1 au in km exact, 1 au exact km, 1 au in kilometers exact value, 1 au exact value in km, 1 au in light years exact value, 1 astronomical unit in miles exact, 1 au in million miles, or exact value of 1 au in km nasa. The exact definition of 1 au in km iau provides a precise reference for astronomical calculations. Learn how to calculate au using this definition.
How Our Astronomical Unit Calculator Works
Our astronomical unit calculator uses the International Astronomical Union's (IAU) 2012 definition, which fixed the astronomical unit as exactly 149,597,870,700 meters. When you enter a distance value in any unit, the calculator first converts it to meters, then displays the equivalent in astronomical units and all other supported units.
Conversion Formulas
Astronomical Unit Definition:1 au = 149,597,870,700 m (exactly)AU to Kilometers:km = au × 149,597,870.7AU to Light Years:ly = au × 0.000015813AU to Parsecs:pc = au × 0.000004848All conversions are based on the IAU 2012 standard definition and international astronomical conventions.
What is an Astronomical Unit?
An astronomical unit (symbol: au) is a unit of length used primarily in astronomy to measure distances within the Solar System. It was originally defined as the average distance between Earth and the Sun, though the IAU now defines it as exactly 149,597,870,700 meters.
Historical Definition
Originally, the astronomical unit was defined as the average distance between Earth and the Sun, approximately 150 million kilometers. This made it convenient for expressing distances within the Solar System.
Average Earth-Sun distance ≈ 1 au
Modern Definition (IAU 2012)
The IAU fixed the astronomical unit as exactly 149,597,870,700 meters in 2012. This provides a precise, unchanging reference for astronomical calculations, independent of Earth's orbital variations.
1 au = 149,597,870,700 m (exact)
History of the Astronomical Unit
The measurement of the astronomical unit has a long and fascinating history:
- 1672: Cassini and Richer made the first rigorous measurement using parallax, achieving a value about 92.5% of the modern value
- Parallax Method: Scientists measured the solar parallax (the angle subtended by Earth's radius at the Sun-Earth distance) and used trigonometry
- Modern Methods: Radar and telemetry from space missions provided increasingly accurate measurements
- 2012: The IAU fixed the value as exactly 149,597,870,700 meters, making it a constant rather than a measured quantity
Astronomical Unit vs. Light Year vs. Parsec
These three units serve different purposes in astronomy:
Astronomical Unit (au)
Best for Solar System distances. 1 au = 149,597,870,700 m. Light travels this distance in about 8 minutes 20 seconds.
Use: Planet distances, asteroid orbits
Light Year (ly)
Distance light travels in one year. 1 ly ≈ 9.461 × 10¹⁵ m ≈ 63,241 au. Used for interstellar distances.
Use: Star distances, galaxy measurements
Parsec (pc)
Distance at which 1 au subtends 1 arcsecond. 1 pc ≈ 206,264.8 au ≈ 3.26 ly. Used in stellar astronomy.
Use: Stellar distances, parallax measurements
Practical Applications
This calculator is essential for various real-world applications:
Astronomy & Space Science
Convert distances for astronomy research, space mission planning, and understanding planetary orbits. Essential for calculating travel times and orbital mechanics in the Solar System.
Education & Learning
Help students understand the scale of the Solar System. Convert between familiar units (km, miles) and astronomical units to visualize planetary distances.
Space Mission Planning
Convert distances for planning space missions, calculating travel times, and understanding the scale of interplanetary distances. Essential for mission design and navigation.
Research & Publications
Convert measurements for scientific papers, research calculations, and astronomical data analysis. Ensure accurate conversions using the IAU standard definition.
Sources & References
- International Astronomical Union (IAU) - Resolution B2 (2012)Official definition: 1 au = 149,597,870,700 m exactly
- National Institute of Standards and Technology (NIST) - Guide for the Use of the International System of UnitsNon-SI units accepted for use with SI, including astronomical unit
- NASA Space Science Data Coordinated Archive - Solar System Distance MeasurementsPlanetary distances and orbital data using astronomical units
Need other conversion tools? Check out our length converter and light year conversion.
Get Custom Calculator for Your PlatformAstronomical Unit Calculator Examples
Input:
- Distance: 1 astronomical unit
Conversion Steps:
- Start with 1 au
- Convert to meters: 1 × 149,597,870,700 = 149,597,870,700 m
- Convert to kilometers: 149,597,870,700 ÷ 1,000 = 149,597,870.7 km
- Convert to miles: 149,597,870,700 ÷ 1,609.344 = 92,955,807.273 mi
- Convert to light years: 149,597,870,700 ÷ 9.461×10¹⁵ = 0.000015813 ly
Result: 1 au = 149,597,870.7 km = 92,955,807 miles
1 astronomical unit equals approximately 149.6 million kilometers, 93 million miles, or 0.000015813 light years.
Input:
- Distance: 5.2 astronomical units
- Context: Jupiter's average distance from the Sun
Conversion Steps:
- Start with 5.2 au
- Convert to meters: 5.2 × 149,597,870,700 = 777,908,927,640 m
- Convert to kilometers: 777,908,927,640 ÷ 1,000 = 777,908,927.64 km
- Convert to miles: 777,908,927,640 ÷ 1,609.344 = 483,638,000 mi
- Convert to light years: 5.2 × 0.000015813 = 0.000082228 ly
Result: 5.2 au = 777,908,927.64 km
Jupiter's average distance from the Sun is 5.2 astronomical units, which equals approximately 778 million kilometers or 484 million miles.
Mars Distance
1.5 au ≈
224.4 million km
Saturn Distance
9.5 au ≈
1.42 billion km
1 Light Year
1 ly =
63,241 au
Frequently Asked Questions
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