A light-year is the distance light travels in a Julian year.
Light-years to Zettameters Converter — ly to Zm
Convert Light-year (ly) to Zettameter (Zm) using the exact conversion factor (1 light-year = 0.0000094607 zettameter). See the formula, worked examples, conversion table, history, and common uses.
Light-years to Zettameters 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.
Zettameter is 1e+21 meter units.
Result = input x 9.46073047e+15 / 1e+21.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Light-years to Zettameters
Light-year and Zettameter both measure length. Light-year is most often used for measuring distances to stars and galaxies.
Formula
zettameters = light-years × 0.00000946073047258
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 zettameter equals 1e+21 base units, so dividing one by the other gives the direct light-year-to-zettameter factor of 0.00000946073047258.
Simple example
1 ly × 0.000009460730473 = 0.0000094607 Zm
1 light-year = 0.0000094607 zettameters.
Real-world example
10 ly × 0.000009460730473 = 0.0000946073 Zm
10 light-years = 0.0000946073 zettameters.
Conversion table
| Light-year (ly) | Zettameter (Zm) |
|---|---|
| 1 ly | 0.0000094607 Zm |
| 5 ly | 0.0000473037 Zm |
| 10 ly | 0.0000946073 Zm |
| 21.0975 ly | 0.0001995978 Zm |
| 42.195 ly | 0.0003991955 Zm |
| 100 ly | 0.000946073 Zm |
Reverse conversion: Zettameter to Light-year
0.0000094607 Zm × 105700.0834 = 0.999996779 ly
0.0000094607 zettameters = 0.999996779 light-years.
light-years = zettameters × 105700.083402
For a page dedicated to this direction, see Zettameter 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 Zettameter (Zm)
Zettameter is 1e+21 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 zettameters are in 1 light-year?
1 light-year equals 0.0000094607 zettameters, using the exact defined conversion factor rather than an estimate.
How do I convert light-year to zettameter?
Multiply the light-year value by 0.000009460730473. The converter above does this instantly to whatever precision you set.
How do I convert zettameter back to light-year?
Use the reverse factor: 1 zettameter equals 105,700.0834 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 zettameter?
Zettameter (Zm) is a unit of length.
Is the light-year to zettameter 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.