The US survey foot is 1200/3937 meters and is retained for legacy land records.
US survey feet to Light-years Converter — ftUS to ly
Convert US survey foot (ftUS) to Light-year (ly) using the exact conversion factor (1 us survey foot = 3.221745e-17 light-year). See the formula, worked examples, conversion table, history, and common uses.
US survey feet to Light-years converter
Converter
Length Converter
Convert SI, imperial, US customary, astronomical, scientific, and historical length units.
Context values
Some unit families need one extra value for a physically accurate result.
A light-year is the distance light travels in a Julian year.
Result = input x 0.3048006096 / 9.46073047e+15.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting US survey feet to Light-years
US survey foot and Light-year both measure length. Specifically: The US survey foot is 1200/3937 meters and is retained for legacy land records, and a light-year is the distance light travels in a Julian year.
Formula
light-years = us survey feet × 3.221745e-17
This factor comes from each unit's defined relationship to the category's base unit: 1 us survey foot equals 0.304800609601 base units, and 1 light-year equals 9.46073e+15 base units, so dividing one by the other gives the direct us survey foot-to-light-year factor of 3.221745e-17.
Simple example
1 ftUS × 3.221745e-17 = 3.221745e-17 ly
1 us survey foot = 3.221745e-17 light-years.
Real-world example
10 ftUS × 3.221745e-17 = 3.221745e-16 ly
10 us survey feet = 3.221745e-16 light-years.
Conversion table
| US survey foot (ftUS) | Light-year (ly) |
|---|---|
| 1 ftUS | 3.221745e-17 ly |
| 5 ftUS | 1.610872e-16 ly |
| 10 ftUS | 3.221745e-16 ly |
| 21.0975 ftUS | 6.797076e-16 ly |
| 42.195 ftUS | 1.359415e-15 ly |
| 100 ftUS | 3.221745e-15 ly |
Reverse conversion: Light-year to US survey foot
3.221745e-17 ly × 3.103908e+16 = 1.000000004 ftUS
3.221745e-17 light-years = 1.000000004 us survey feet.
us survey feet = light-years × 3.103908e+16
For a page dedicated to this direction, see Light-year to US survey foot.
Understanding the US survey foot (ftUS)
The US survey foot is 1200/3937 meters and is retained for legacy land records.
Understanding the Light-year
Light-year (ly) measures distance. A light-year is the distance light travels in one Julian year (365.25 days) in vacuum: exactly 9,460,730,472,580,800 meters. It is classified as a Non-SI unit (astronomical).
Where it's used: Used internationally in astronomy and popular science for interstellar distances.
Uses of the Light-year today
- Measuring distances to stars and galaxies
- Popular science communication about the scale of the universe
- Astrophysics research
History of the Light-year
The light-year emerged in 19th-century astronomy as scientists began measuring stellar distances via parallax (Friedrich Bessel's 1838 measurement of 61 Cygni is often cited as the first reliable stellar distance). Expressing these vast distances in light-travel-time became a practical convention, and the unit's value follows directly from the defined speed of light and the length of a Julian year.
Historical origin. Light-year was not the invention of a single named person; it developed through the process described above.
Light-year — sources
- IAU — Light year definition — Defines the light-year via the Julian year and the speed of light.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many light-years are in 1 us survey foot?
1 us survey foot equals 3.221745e-17 light-years, using the exact defined conversion factor rather than an estimate.
How do I convert us survey foot to light-year?
Multiply the us survey foot value by 3.221745e-17. The converter above does this instantly to whatever precision you set.
How do I convert light-year back to us survey foot?
Use the reverse factor: 1 light-year equals 3.103908e+16 us survey feet. You can also use the swap control in the converter above to flip the direction instantly.
What is a us survey foot?
US survey foot (ftUS) is a unit of length.
What is a light-year?
Light-year (ly) measures distance. A light-year is the distance light travels in one Julian year (365.25 days) in vacuum: exactly 9,460,730,472,580,800 meters. It is classified as a Non-SI unit (astronomical).
Is the us survey foot to light-year conversion exact?
Yes. A light-year is the distance light travels in one Julian year (365.25 days) in vacuum: exactly 9,460,730,472,580,800 meters. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.