Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Unit Converters
Light Years to Kilometers Converter
kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
A light year is a distance, not a birthday. It is how far light travels in one Julian year: about 9.461 trillion km. Proxima Centauri is 4.25 ly, not “four years away in a 747.”
Light years
ly → km
9.4607e12 km
1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
- You typed
- 1 ly
- One km is
- 1.0570e-13 ly
- How it’s calculated
- kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Light years
Length of the repayment schedule.
How this calculator works
A light year is a distance, not a birthday. It is how far light travels in one Julian year: about 9.461 trillion km. Proxima Centauri is 4.25 ly, not “four years away in a 747.” kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year). Example: 1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
Example: 1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
When to use this Light Years to Kilometers
Common use cases
- A light year is a distance, not a birthday. It is how far light travels in one Julian year: about 9.461 trillion km. Proxima Centauri is 4.25 ly, not “four years away in a 747.”
- Sanity-check with this case: 1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
- The relationship is: kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
Localized examples
- Unit Converters: the example on this page uses the same formula as the widget.
What you get
- Fields: Light years
- kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
- Example on the page: 1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
How to Convert Light Years to Kilometers Step-by-Step
- 1Enter Light years. Use the values you have, not a catalog average, unless that is all you know.
- 2kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
- 3Worked case: 1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
- 4Check which dictionary the other person is using — US or UK, decimal or 1,024 — then trust the number.
Governing formula
kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).
1 ly ≈ 9.461 × 10¹² km. Proxima at 4.246 ly ≈ 4.017 × 10¹³ km.
Example: set Light years = 1, then read the result.
Variable definitions
- value
Light years
The “Light years” field. Default 1; typical range 0–1000.
- The conversion (kilometers = light years × 9.4607304725808 × 10¹² (IAU Julian year).) does not pick US vs UK gallons, SI vs binary megabytes, or Mach at altitude for you. Read the footnote on the page.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
No. 1 pc ≈ 3.26 ly. Convert ly here; do not paste parsecs into this field.
Related calculators
Unit Converters
- Julian Years to SecondsA Julian year is 365.25 days × 86,400 s = 31,557,600 s. Light-years, orbital periods, and IAU constants use this, not 365 or 365.2425. A millisecond of a Julian year is still a lot of seconds if you expand it.
- Nautical Miles to KilometersCharts, flight plans, and AIS tracks use nautical miles because one nmi is one minute of latitude. That is 1.852 km exactly — longer than a statute mile. Do not drop a flight plan into the land-mile converter.
- Parsecs to Light YearsA parsec is the distance at which 1 au subtends one arcsecond — about 3.26156 light years, or 3.085677581×10¹⁶ m. Proxima Centauri at ~1.3 pc is ~4.24 ly. Astronomy papers prefer parsecs; documentaries prefer light years.
- Astronomical Units to KilometersThe IAU 2012 astronomical unit is exactly 149,597,870,700 m — about 149.6 million km. Earth–Sun mean distance sits on that stick. Mars at 1.524 au is not a NASA press-round; it is that constant times 1.524.
- Brown Sugar Cups to GramsPacked light or dark brown sugar is about 220 g per US cup. “Packed” means you pressed it. A loose scoop can miss 30 g and flatten cookies. Light and dark weigh nearly the same; molasses is the flavor, not the scale.
- Cat Years to HumanFirst year ~15, second ~9 more, then about 4 human years per cat year. Indoor cats often outlive the meme. Indoor/outdoor and dental care move this more than the formula.
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4.8
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Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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