A light-year is the distance light travels in a Julian year.
Light-years to Petameters Converter — ly to Pm
Convert Light-year (ly) to Petameter (Pm) using the exact conversion factor (1 light-year = 9.460730473 petameter). See the formula, worked examples, conversion table, history, and common uses.
Light-years to Petameters 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.
Petameter is 1000000000000000 meter units.
Result = input x 9.46073047e+15 / 1e+15.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Light-years to Petameters
Light-year and Petameter both measure length. Light-year is most often used for measuring distances to stars and galaxies.
Formula
petameters = light-years × 9.46073047258
This factor comes from each unit's defined relationship to the category's base unit: 1 light-year equals 9.46073e+15 base units, and 1 petameter equals 1e+15 base units, so dividing one by the other gives the direct light-year-to-petameter factor of 9.46073047258.
Simple example
1 ly × 9.460730473 = 9.460730473 Pm
1 light-year = 9.460730473 petameters.
Real-world example
10 ly × 9.460730473 = 94.60730473 Pm
10 light-years = 94.60730473 petameters.
Conversion table
| Light-year (ly) | Petameter (Pm) |
|---|---|
| 1 ly | 9.460730473 Pm |
| 5 ly | 47.30365236 Pm |
| 10 ly | 94.60730473 Pm |
| 21.0975 ly | 199.5977611 Pm |
| 42.195 ly | 399.1955223 Pm |
| 100 ly | 946.0730473 Pm |
Reverse conversion: Petameter to Light-year
9.460730473 Pm × 0.1057000834 = 1 ly
9.460730473 petameters = 1 light-years.
light-years = petameters × 0.105700083402
For a page dedicated to this direction, see Petameter to Light-year.
Understanding the Light-year
Light-year (ly) measures distance. A light-year is the distance light travels in one Julian year (365.25 days) in vacuum: exactly 9,460,730,472,580,800 meters. It is classified as a Non-SI unit (astronomical).
Where it's used: Used internationally in astronomy and popular science for interstellar distances.
Uses of the Light-year today
- Measuring distances to stars and galaxies
- Popular science communication about the scale of the universe
- Astrophysics research
History of the Light-year
The light-year emerged in 19th-century astronomy as scientists began measuring stellar distances via parallax (Friedrich Bessel's 1838 measurement of 61 Cygni is often cited as the first reliable stellar distance). Expressing these vast distances in light-travel-time became a practical convention, and the unit's value follows directly from the defined speed of light and the length of a Julian year.
Historical origin. Light-year was not the invention of a single named person; it developed through the process described above.
Understanding the Petameter (Pm)
Petameter is 1000000000000000 meter units.
Light-year — sources
- IAU — Light year definition — Defines the light-year via the Julian year and the speed of light.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many petameters are in 1 light-year?
1 light-year equals 9.460730473 petameters, using the exact defined conversion factor rather than an estimate.
How do I convert light-year to petameter?
Multiply the light-year value by 9.460730473. The converter above does this instantly to whatever precision you set.
How do I convert petameter back to light-year?
Use the reverse factor: 1 petameter equals 0.1057000834 light-years. You can also use the swap control in the converter above to flip the direction instantly.
What is a light-year?
Light-year (ly) measures distance. A light-year is the distance light travels in one Julian year (365.25 days) in vacuum: exactly 9,460,730,472,580,800 meters. It is classified as a Non-SI unit (astronomical).
What is a petameter?
Petameter (Pm) is a unit of length.
Is the light-year to petameter conversion exact?
Yes. A light-year is the distance light travels in one Julian year (365.25 days) in vacuum: exactly 9,460,730,472,580,800 meters. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Where is the light-year still used today?
Used internationally in astronomy and popular science for interstellar distances.