Convert Astronomical Unit to Parsec
Convert astronomical units to parsecs instantly. 1 astronomical unit = 4.848137e-6 parsec — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Parsec 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.
Parsec
A parsec (parallax-second) is a distance unit equal to 648,000/π astronomical units — approximately 3.086×10¹⁶ m (3.26 light years). It is the standard distance unit in professional astronomy.
Defined as the distance at which one astronomical unit subtends an angle of one arcsecond. IAU Resolution B2 in 2015 made this an exact definition: 1 pc = (648,000/π) AU.
Parsecs are used in professional astronomy for stellar distances (Proxima Centauri ≈ 1.3 pc), galactic-scale distances (with prefixes kiloparsec and megaparsec), and parallax measurements. Standard since the early 20th century.
Concept introduced by Herbert Hall Turner in 1913; exact definition via the AU adopted by IAU Resolution B2 in 2015.
Astronomical Unit to Parsec conversion formula
The relationship between astronomical units and parsecs:
To convert astronomical units to parsecs, multiply the value in astronomical units by 4.848137e-6. To reverse, multiply parsecs by 206264.8062470964.
How to use this converter
Type a value into the calculator. The result in parsecs updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Parsec to Astronomical Unit converter for the reverse direction.
Step-by-step: convert astronomical units to parsecs
- Write down the value in astronomical units (AU).
- Multiply that value by the factor 4.848137e-6.
- The product is the equivalent value in parsecs (pc).
- To reverse, multiply the parsec value by 206264.8062470964.
Worked examples
Example 1 — Convert 1 AU to pc:
1 × 4.848137e-6 = 4.848137e-6 pc
Example 2 — Convert 100 AU to pc:
100 × 4.848137e-6 = 0.0004848137 pc
Astronomical Unit to Parsec conversion table
Standard reference values for converting astronomical units to parsecs:
| Astronomical Unit [AU] | Parsec [pc] |
|---|---|
| 0.01 | 4.848137e-8 |
| 0.1 | 4.848137e-7 |
| 1 | 4.848137e-6 |
| 2 | 9.696274e-6 |
| 3 | 1.454441e-5 |
| 4 | 1.939255e-5 |
| 5 | 2.424068e-5 |
| 10 | 4.848137e-5 |
| 20 | 9.696274e-5 |
| 30 | 0.0001454441 |
| 40 | 0.0001939255 |
| 50 | 0.0002424068 |
| 100 | 0.0004848137 |
| 500 | 0.0024240684 |
| 1000 | 0.0048481368 |
Frequently asked questions
How many parsecs is 1 astronomical unit?
How do I convert astronomical units to parsecs?
How do I convert parsecs back to astronomical units?
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Sources & references
Conversion factor (1 AU = 4.848137e-6 pc) 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.