Light-Years to Miles

Light-years and miles

The light-year is the distance light travels in vacuum in one Julian year (365.25 days): exactly 9,460,730,472,580,800 meters by the IAU definition. Astronomers and science writers use it for distances between stars; professionals more often use parsecs.

The international mile is exactly 1,760 yards, or 1,609.344 meters, under the 1959 yard and pound agreement. Road distances and speed limits in the United States and United Kingdom use miles.

Worked example

Convert 4.24 ly: 4.24 × 5,878,625,373,000 = 24,925,371,580,000, so 4.24 light-years is 24,925,371,580,000 miles. Likewise 2 ly = 11,757,250,750,000 mi.

Estimating in your head

Multiply by 5,900,000,000,000 for a quick figure; it is off by about 0.4%. For 4.24 ly that gives 25,000,000,000,000 mi, against 24,925,400,000,000 exactly.

Going the other way

To convert miles to light-years, divide by 5,878,625,373,000 (or multiply by 1.70107795023 × 10^-13).

mi = ly × 5,878,625,373,000

1 ly = ≈ 9.460730473 × 10^15 m and 1 mi = 1,609.344 m, both by definition, so the factor is their ratio: 5,878,625,373,000 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.