🌌 Astronomical Conversion Calculator 2026
Convert cosmic distances — light years, parsecs, astronomical units & more
Conversion Result
3.26156 light years
1 parsec = 3.26156 light years
Understanding Astronomical Units
🌟 Light Year (ly)
Distance light travels in one year ≈ 9.461 trillion km. Based on Julian year (365.25 days). Used for stellar and galactic distances.
🔭 Parsec (pc)
Distance at which 1 AU subtends 1 arcsecond ≈ 3.26 ly ≈ 30.86 trillion km. Standard unit in professional astronomy.
☀️ Astronomical Unit (AU)
Average Earth-Sun distance = 149,597,870.7 km exactly. Used for solar system distances. Light takes 8.3 minutes to travel 1 AU.
💫 Light Second/Minute/Hour
Distance light travels in given time. Light second ≈ 299,792 km. Moon is ~1.3 light seconds away. Sun is ~8.3 light minutes away.
Astronomical Distance Reference
| Unit | Symbol | In Kilometers | Example Distance |
|---|---|---|---|
| Light Second | ls |
299,792.458 | Moon: 1.3 ls |
| Light Minute | lm |
17,987,547.48 | Sun: 8.3 lm |
| Astronomical Unit | AU |
149,597,870.7 | Sun-Earth: 1 AU |
| Light Hour | lh |
1,079,252,848.8 | Saturn: ~1.3 lh |
| Light Day | ld |
25,902,068,371.2 | Voyager 1: ~23 ld |
| Light Year | ly |
9.461×10¹² | Proxima Centauri: 4.24 ly |
| Parsec | pc |
3.086×10¹³ | Nearest stars: 1-4 pc |
Frequently Asked Questions
What is a light year?
A light year is the distance light travels in one year in vacuum ≈
9.461 trillion kilometers (9.461×10¹² km). It's based on the Julian year of exactly
365.25 days and light speed of 299,792.458 km/s.
How do I convert light years to kilometers?
Multiply by 9.461×10¹². Formula: km = light years ×
9,460,730,472,580.8. Example: 4.24 ly (Proxima Centauri) = 40.1 trillion km.
What is a parsec?
A parsec (parallax arcsecond) is the distance at which 1 AU
subtends an angle of 1 arcsecond. 1 parsec = 3.26156 light years = 30.857 trillion km.
Preferred by astronomers for technical calculations.
How do I convert parsecs to light years?
Multiply by 3.26156. Formula: ly = parsecs × 3.26156. Example: 10
parsecs = 32.6156 light years. The Milky Way is ~30,000 parsecs (100,000 ly) across.
What is an Astronomical Unit (AU)?
The Astronomical Unit is defined as exactly 149,597,870.7
km—approximately the average Earth-Sun distance. Used for solar system distances. Pluto is
about 40 AU from the Sun.
How long does light take to travel 1 AU?
Light takes approximately 8 minutes 19 seconds (499 seconds) to
travel 1 AU. This means when you see the Sun, you see it as it was ~8 minutes ago.
What's the difference between Julian and tropical light years?
Julian light year uses 365.25 days (IAU standard).
Tropical light year uses ~365.24219 days (one orbit relative to vernal equinox).
Difference is tiny—about 0.002%.
How far is the nearest star?
Proxima Centauri is 4.24 light years (1.30 parsecs, 268,770 AU)
away. Light from Proxima takes 4.24 years to reach Earth. At current spacecraft speeds, it would take
~73,000 years to reach.
What is a light second used for?
A light second = 299,792.458 km. Useful for close astronomical
distances: Moon ≈ 1.28 ls, Mars varies 3-22 light minutes, causing communication delays for rovers.
How big is our solar system in light hours?
The solar system (to Pluto's orbit) is about 5.5 light hours
across. The Voyager 1 probe (farthest human-made object) is about 23.5 light hours from Earth as of
2026.
Why do astronomers prefer parsecs over light years?
Parsecs are directly derived from parallax measurements—the
primary method for measuring stellar distances. Distance in parsecs = 1/parallax angle in arcseconds.
This makes calculations simpler.
How do I convert kilometers to light years?
Divide by 9.461×10¹². Formula: ly = km ÷ 9,460,730,472,580.8.
Example: 1 million km = 1.057×10⁻⁷ light years (a very small fraction).
What is a kiloparsec and megaparsec?
1 kiloparsec (kpc) = 1,000 pc = 3,262 ly. 1 megaparsec
(Mpc) = 1 million pc = 3.26 million ly. Used for galaxy and cosmological distances.
How far is the Andromeda Galaxy?
Andromeda (M31) is about 2.537 million light years (778 kpc)
away—the nearest major galaxy. Light we see from Andromeda left when early humans first appeared on
Earth.
Can I convert between light time units easily?
Yes! Light second × 60 = light minute. Light minute × 60 = light hour. Light hour ×
24 = light day. Light day × 365.25 = light year (Julian).
What's faster than light speed?
Nothing with mass can reach or exceed light speed (c) per special
relativity. Light speed = 299,792.458 km/s exactly. This limit defines all astronomical distance
calculations involving light travel time.
How accurate is this astronomical converter?
Uses IAU-standard values: AU = 149,597,870.7 km exactly, c = 299,792.458 km/s
exactly, Julian year = 31,557,600 seconds. Double-precision provides 15-16 significant digits.