A parsec is about 3.26156 light-years.
Parsecs to Kilometers Converter — pc to km
Convert Parsec (pc) to Kilometer (km) using the exact conversion factor (1 parsec = 3.085678e+13 kilometer). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Parsecs to Kilometers converter
Converter
Length Converter
Convert SI, imperial, US customary, astronomical, scientific, and historical length units.
Context values
Some unit families need one extra value for a physically accurate result.
Kilometer is 1000 meter units.
Result = input x 3.08567758e+16 / 1000.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Parsecs to Kilometers
Parsec and Kilometer both measure length. Parsec is typically associated with standard distance unit throughout professional astronomy worldwide, while Kilometer is typically associated with standard road, distance, and mapping unit in nearly every country except the United States.
Formula
kilometers = parsecs × 3.085678e+13
This factor comes from each unit's defined relationship to the category's base unit: 1 parsec equals 3.085678e+16 base units, and 1 kilometer equals 1000 base units, so dividing one by the other gives the direct parsec-to-kilometer factor of 3.085678e+13.
Simple example
1 pc × 3.085678e+13 = 3.085678e+13 km
1 parsec = 3.085678e+13 kilometers.
Real-world example
10 pc × 3.085678e+13 = 3.085678e+14 km
10 parsecs = 3.085678e+14 kilometers.
Conversion table
| Parsec (pc) | Kilometer (km) |
|---|---|
| 1 pc | 3.085678e+13 km |
| 5 pc | 1.542839e+14 km |
| 10 pc | 3.085678e+14 km |
| 21.0975 pc | 6.510008e+14 km |
| 42.195 pc | 1.302002e+15 km |
| 100 pc | 3.085678e+15 km |
Reverse conversion: Kilometer to Parsec
3.085678e+13 km × 3.240779e-14 = 1.000000136 pc
3.085678e+13 kilometers = 1.000000136 parsecs.
parsecs = kilometers × 3.240779e-14
For a page dedicated to this direction, see Kilometer to Parsec.
Parsec vs. Kilometer
| Aspect | Parsec | Kilometer |
|---|---|---|
| Family | non-SI unit used in astronomy | SI derived (metric prefix) unit |
| Typical use | Measuring distances to nearby stars via parallax | Road signage, speed limits, and vehicle odometers outside the US |
| Where it's used | Standard distance unit throughout professional astronomy worldwide | Standard road, distance, and mapping unit in nearly every country except the United States |
Understanding the Parsec
Parsec (pc) measures astronomical distance. The distance at which one astronomical unit subtends an angle of one arcsecond — approximately 3.26 light-years, or about 3.086 × 10¹⁶ meters. It is classified as a non-SI unit used in astronomy.
Where it's used: Standard distance unit throughout professional astronomy worldwide
Uses of the Parsec today
- Measuring distances to nearby stars via parallax
- Galactic and extragalactic distance scales in astrophysics research
History of the Parsec
The name is a portmanteau of 'parallax' and 'arcsecond,' reflecting how the unit is defined directly from the parallax method astronomers use to measure stellar distances: the tiny apparent shift in a nearby star's position as Earth orbits the Sun.
Historical origin. Parsec was not the invention of a single named person; it developed through the process described above.
Understanding the Kilometer
Kilometer (km) measures distance. A kilometer is 1,000 meters — the meter is the SI base unit of length. It is classified as a SI derived (metric prefix) unit.
Where it's used: Standard road, distance, and mapping unit in nearly every country except the United States
Uses of the Kilometer today
- Road signage, speed limits, and vehicle odometers outside the US
- Geographic and mapping distances
- Endurance sports (marathons are measured in kilometers internationally, though the marathon distance itself is a fixed value in both systems)
History of the Kilometer
The meter was defined during the French Revolutionary metric reforms as one ten-millionth of the distance from the North Pole to the Equator along a meridian through Paris. 'Kilo-' is simply the SI prefix for 1,000, making the kilometer a direct decimal multiple.
The meter itself has been redefined several times as measurement precision improved — from a physical platinum-iridium bar (1889) to a krypton-86 wavelength (1960) to its current definition (1983) as the distance light travels in a fixed fraction of a second.
Historical origin. Kilometer was not the invention of a single named person; it developed through the process described above.
Parsec — sources
- IAU (International Astronomical Union) — parsec definition — Standard astronomical definition of the parsec via stellar parallax.
Kilometer — sources
- BIPM — The metre (SI base unit) — Current definition and history of the meter.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilometers are in 1 parsec?
1 parsec equals 3.085678e+13 kilometers, using the exact defined conversion factor rather than an estimate.
How do I convert parsec to kilometer?
Multiply the parsec value by 3.085678e+13. The converter above does this instantly to whatever precision you set.
How do I convert kilometer back to parsec?
Use the reverse factor: 1 kilometer equals 3.240779e-14 parsecs. You can also use the swap control in the converter above to flip the direction instantly.
What is a parsec?
Parsec (pc) measures astronomical distance. The distance at which one astronomical unit subtends an angle of one arcsecond — approximately 3.26 light-years, or about 3.086 × 10¹⁶ meters. It is classified as a non-SI unit used in astronomy.
What is a kilometer?
Kilometer (km) measures distance. A kilometer is 1,000 meters — the meter is the SI base unit of length. It is classified as a SI derived (metric prefix) unit.
Is the parsec to kilometer conversion exact?
Yes. Both parsec and kilometer are defined by fixed standards rather than physical artifacts, so the factor of 3.085678e+13 used above is exact to as many digits as you choose to display.
Where is the parsec still used today?
Standard distance unit throughout professional astronomy worldwide