Convert Light Year to Sun's Radius
Convert light years to sun's radii instantly. 1 light year = 1.359887e+7 sun's radius — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Sun's Radius to Light Year converter for the reverse conversion.
Units explained
Light Year
A light year is the distance light travels in one Julian year in vacuum — exactly 9,460,730,472,580,800 meters (about 9.46×10¹⁵ m). It is the most common unit for expressing inter-stellar distances in non-technical astronomy.
Defined as the speed of light (299,792,458 m/s, exact) multiplied by one Julian year (365.25 days × 86400 seconds/day). Both factors are exact, making the light year exact by definition.
Light years are used in popular astronomy, science journalism, and stellar distance descriptions. The nearest star (Proxima Centauri) is 4.24 ly away; the Milky Way is about 100,000 ly across.
Concept of distance-as-time used since the 19th century; the modern exact definition follows from the 1983 SI definition of the meter via the speed of light.
Sun's Radius
The Sun's radius is approximately 695,700 km (6.957×10⁸ m), defined as the IAU 2015 nominal solar radius for use in stellar physics and exoplanet research.
The IAU (International Astronomical Union) Resolution B3 in 2015 defined a nominal solar radius of exactly 6.957×10⁸ m to serve as a stable reference, independent of actual measurement-uncertainty variations in the real Sun.
Solar radii are used in stellar physics, exoplanet characterisation, and any context where a star's size is expressed relative to the Sun. Most stellar radius measurements are quoted in solar-radius units rather than meters.
Defined exactly at 6.957×10⁸ m by IAU Resolution B3 in 2015.
Light Year to Sun's Radius conversion formula
The relationship between light years and sun's radii:
To convert light years to sun's radii, multiply the value in light years by 1.359887e+7. To reverse, multiply sun's radii by 7.353555e-8.
How to use this converter
Type a value into the calculator. The result in sun's radii updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Sun's Radius to Light Year converter for the reverse direction.
Step-by-step: convert light years to sun's radii
- Write down the value in light years (ly).
- Multiply that value by the factor 1.359887e+7.
- The product is the equivalent value in sun's radii (R☉).
- To reverse, multiply the sun's radius value by 7.353555e-8.
Worked examples
Example 1 — Convert 1 ly to R☉:
1 × 1.359887e+7 = 1.359887e+7 R☉
Example 2 — Convert 100 ly to R☉:
100 × 1.359887e+7 = 1.359887e+9 R☉
Light Year to Sun's Radius conversion table
Standard reference values for converting light years to sun's radii:
| Light Year [ly] | Sun's Radius [R☉] |
|---|---|
| 0.01 | 135988.6513235705 |
| 0.1 | 1359886.513235705 |
| 1 | 1.359887e+7 |
| 2 | 2.719773e+7 |
| 3 | 4.07966e+7 |
| 4 | 5.439546e+7 |
| 5 | 6.799433e+7 |
| 10 | 1.359887e+8 |
| 20 | 2.719773e+8 |
| 30 | 4.07966e+8 |
| 40 | 5.439546e+8 |
| 50 | 6.799433e+8 |
| 100 | 1.359887e+9 |
| 500 | 6.799433e+9 |
| 1000 | 1.359887e+10 |
Frequently asked questions
How many sun's radii is 1 light year?
How do I convert light years to sun's radii?
How do I convert sun's radii back to light years?
How many sun's radii is 100 light years?
Popular length unit conversions
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Metric / SI (4 units)
Imperial / US Customary (4 units)
Astronomical (8 units)
Sources & references
Conversion factor (1 ly = 1.359887e+7 R☉) 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.