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Length

Convert light years to fathoms

1 ly=5.1732e15ftm

Use the converter below to change any light years value into fathoms instantly — with formula, conversion table, and real-world examples.

5.1732e15

Conversion formula

Forward
fathoms = light years × 5.1732e15
Reverse
light years = fathoms × 1.9330e-16

Example: 10 ly × 5.1732e15 = 5.1732e16 ftm.

About both units

From

Light Year

ly

A light year is the distance light travels in one Julian year — approximately 9.461 × 10¹⁵ meters, or 63,241 AU. It is used in astronomy to describe distances between stars and galaxies. The nearest star to the Sun, Proxima Centauri, is 4.24 light years away.

Real-world: Proxima Centauri, the nearest star beyond the Sun, is 4.24 ly away. The Milky Way is about 100,000 ly across.
Read full light year reference →
To

Fathom

ftm

The fathom equals exactly 6 feet or 1.8288 meters. It is the traditional marine unit for water depth, used on older nautical charts and in recreational sailing. Modern charts mark depths in metres, but fathoms still appear in maritime literature and older US charts.

Real-world: A "mark twain" reading — made famous by the Mississippi riverboats — meant 2 fathoms (3.66 m) of water, the minimum safe depth.
Read full fathom reference →

Light Year to Fathom conversion table

Common light years to fathoms values for quick reference.

Light Year (ly)Fathom (ftm)
1 ly5.1732e15 ftm
5 ly2.5866e16 ftm
10 ly5.1732e16 ftm
25 ly1.2933e17 ftm
50 ly2.5866e17 ftm
100 ly5.1732e17 ftm
250 ly1.2933e18 ftm
500 ly2.5866e18 ftm
1,000 ly5.1732e18 ftm
5,000 ly2.5866e19 ftm

Tips & common mistakes

Quick tips

  • The light year is a unit of distance, not time, despite the name.
  • Professional astronomers usually prefer parsecs (1 pc ≈ 3.26 ly) for precision work.
  • Light from the Andromeda galaxy takes 2.5 million years to reach us — we see it as it was 2.5 Myr ago.

Avoid these

  • Confusing light year with light second — light second ≈ 300,000 km.
  • Treating light years as time rather than distance in casual conversation.
  • Using light years for solar-system distances — use astronomical units (AU) instead.

Frequently asked questions

How many fathoms in a light year?
One light year equals 5.1732e15 fathoms.
How do I convert light years to fathoms?
Multiply the light year value by 5.1732e15 to get the equivalent in fathoms.
What is 100 light years in fathoms?
100 light years equals 5.1732e17 fathoms.
Is a light year bigger than a fathom?
Yes. 1 light year equals 5.1732e15 fathoms, so one light year is larger.
How to convert light years to fathoms without a calculator?
Multiply by 5.1732e15 for a quick estimate; use a calculator for precise results.

Related length conversions

📊 See full comparison matrix →

More from Light Year

ly → m
1 = 9.4607e15 m
ly → km
1 = 9,460,700,000,000 km
ly → cm
1 = 9.4607e17 cm
ly → mm
1 = 9.4607e18 mm
ly → mi
1 = 5,878,606,438,399.75 mi
ly → yd
1 = 1.0346e16 yd
ly → ft
1 = 3.1039e16 ft
ly → in
1 = 3.7247e17 in

More to Fathom

m → ftm
1 = 0.5468 ftm
km → ftm
1 = 546.807 ftm
cm → ftm
1 = 0.005468 ftm
mm → ftm
1 = 0.0005468 ftm
mi → ftm
1 = 880 ftm
yd → ftm
1 = 0.5 ftm
ft → ftm
1 = 0.1667 ftm
in → ftm
1 = 0.01389 ftm

Conversions in other categories

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