Convert Astronomical Unit to Millimeter
Convert astronomical units to millimeters instantly. 1 astronomical unit = 1.495979e+14 millimeter — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Millimeter to Astronomical Unit converter for the reverse conversion.
Units explained
Astronomical Unit
The astronomical unit (AU) is a unit of length equal to exactly 149,597,870,700 meters, approximately the average distance from Earth to the Sun. It is the fundamental unit for distance within the solar system.
The AU was originally defined as the semi-major axis of Earth's orbit. In 2012, IAU Resolution B2 redefined the AU as exactly 149,597,870,700 meters, severing its dependence on the actual fluctuating Earth–Sun distance.
AUs are used to express distances within the solar system (Mars: 1.5 AU, Pluto: ~40 AU at perihelion), exoplanet orbital radii, and other planetary-scale distances. Standard in planetary science and astronomy.
Original definition tied to Earth's orbit (Newton, 17th century); fixed at exactly 149,597,870,700 m by IAU Resolution B2 in 2012.
Millimeter
A millimeter is a metric unit of length equal to one thousandth of a meter (1/1000 m). It is the standard small-scale unit in the SI system and is widely used wherever sub-centimeter precision matters.
The millimeter was defined alongside the meter when France adopted the metric system in 1795, using the standard SI prefix milli- (from Latin mille, "thousand") to denote one-thousandth.
Millimeters are used in engineering drawings, machining, manufacturing, paper sizes, rainfall measurement, and any context where dimensions below one centimeter need to be specified clearly. Most rulers worldwide are marked in millimeters.
Adopted in 1795 in France as part of the original metric system; standardized internationally by the Metre Convention in 1875 and confirmed in the SI in 1960.
Astronomical Unit to Millimeter conversion formula
The relationship between astronomical units and millimeters:
To convert astronomical units to millimeters, multiply the value in astronomical units by 1.495979e+14. To reverse, multiply millimeters by 6.684587e-15.
How to use this converter
Type a value into the calculator. The result in millimeters updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Millimeter to Astronomical Unit converter for the reverse direction.
Step-by-step: convert astronomical units to millimeters
- Write down the value in astronomical units (AU).
- Multiply that value by the factor 1.495979e+14.
- The product is the equivalent value in millimeters (mm).
- To reverse, multiply the millimeter value by 6.684587e-15.
Worked examples
Example 1 — Convert 1 AU to mm:
1 × 1.495979e+14 = 1.495979e+14 mm
Example 2 — Convert 100 AU to mm:
100 × 1.495979e+14 = 1.495979e+16 mm
Astronomical Unit to Millimeter conversion table
Standard reference values for converting astronomical units to millimeters:
| Astronomical Unit [AU] | Millimeter [mm] |
|---|---|
| 0.01 | 1.495979e+12 |
| 0.1 | 1.495979e+13 |
| 1 | 1.495979e+14 |
| 2 | 2.991957e+14 |
| 3 | 4.487936e+14 |
| 4 | 5.983915e+14 |
| 5 | 7.479894e+14 |
| 10 | 1.495979e+15 |
| 20 | 2.991957e+15 |
| 30 | 4.487936e+15 |
| 40 | 5.983915e+15 |
| 50 | 7.479894e+15 |
| 100 | 1.495979e+16 |
| 500 | 7.479894e+16 |
| 1000 | 1.495979e+17 |
Frequently asked questions
How many millimeters is 1 astronomical unit?
How do I convert astronomical units to millimeters?
How do I convert millimeters back to astronomical units?
How many millimeters is 100 astronomical units?
Popular length unit conversions
Convert Astronomical Unit to other length units
Show all Astronomical Unit conversions
Metric / SI (4 units)
Imperial / US Customary (4 units)
Astronomical (8 units)
Sources & references
Conversion factor (1 AU = 1.495979e+14 mm) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.