An astronomical unit is the mean Earth-Sun distance.
Astronomical units to Fathoms Converter — AU to ftm
Convert Astronomical unit (AU) to Fathom (ftm) using the exact conversion factor (1 astronomical unit = 81,801,110,400 fathom). See the formula, worked examples, conversion table, history, and common uses.
Astronomical units to Fathoms 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 fathom is six feet.
Result = input x 1.49597871e+11 / 1.8288.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Astronomical units to Fathoms
Astronomical unit and Fathom both measure length. Astronomical unit is most often used for measuring distances within the solar system (planetary orbits).
Formula
fathoms = astronomical units × 81801110400.3
This factor comes from each unit's defined relationship to the category's base unit: 1 astronomical unit equals 149597870700 base units, and 1 fathom equals 1.8288 base units, so dividing one by the other gives the direct astronomical unit-to-fathom factor of 81801110400.3.
Simple example
1 AU × 81801110400 = 81,801,110,400 ftm
1 astronomical unit = 81,801,110,400 fathoms.
Real-world example
10 AU × 81801110400 = 818,011,104,000 ftm
10 astronomical units = 818,011,104,000 fathoms.
Conversion table
| Astronomical unit (AU) | Fathom (ftm) |
|---|---|
| 1 AU | 81,801,110,400 ftm |
| 5 AU | 409,005,552,000 ftm |
| 10 AU | 818,011,104,000 ftm |
| 21.0975 AU | 1.725799e+12 ftm |
| 42.195 AU | 3.451598e+12 ftm |
| 100 AU | 8.180111e+12 ftm |
Reverse conversion: Fathom to Astronomical unit
1 ftm × 1.222477e-11 = 1.222477e-11 AU
1 fathom = 1.222477e-11 astronomical units.
astronomical units = fathoms × 1.222477e-11
For a page dedicated to this direction, see Fathom to Astronomical unit.
Understanding the Astronomical unit
Astronomical unit (AU) measures distance. The astronomical unit is defined as exactly 149,597,870,700 meters, close to the average Earth-Sun distance. It is classified as a Non-SI unit accepted for use with SI (astronomical).
Where it's used: Used internationally in astronomy for solar-system-scale distances.
Uses of the Astronomical unit today
- Measuring distances within the solar system (planetary orbits)
- Astronomical calculations and spacecraft navigation
- Popular science communication about the solar system
History of the Astronomical unit
The astronomical unit originated from 17th-19th century attempts to measure the Earth-Sun distance, refined over time using transits of Venus and later radar and spacecraft ranging.
In 2012, the International Astronomical Union fixed the AU at exactly 149,597,870,700 meters, replacing its earlier definition (tied to gravitational calculations) with a simple fixed distance, independent of the slightly-variable actual Earth-Sun distance.
Historical origin. Astronomical unit was not the invention of a single named person; it developed through the process described above.
Understanding the Fathom (ftm)
A fathom is six feet.
Astronomical unit — sources
- IAU Resolution B2 (2012) — Fixes the astronomical unit at exactly 149,597,870,700 meters.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many fathoms are in 1 astronomical unit?
1 astronomical unit equals 81,801,110,400 fathoms, using the exact defined conversion factor rather than an estimate.
How do I convert astronomical unit to fathom?
Multiply the astronomical unit value by 81801110400. The converter above does this instantly to whatever precision you set.
How do I convert fathom back to astronomical unit?
Use the reverse factor: 1 fathom equals 1.222477e-11 astronomical units. You can also use the swap control in the converter above to flip the direction instantly.
What is a astronomical unit?
Astronomical unit (AU) measures distance. The astronomical unit is defined as exactly 149,597,870,700 meters, close to the average Earth-Sun distance. It is classified as a Non-SI unit accepted for use with SI (astronomical).
What is a fathom?
Fathom (ftm) is a unit of length.
Is the astronomical unit to fathom conversion exact?
Yes. The astronomical unit is defined as exactly 149,597,870,700 meters, close to the average Earth-Sun distance. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Where is the astronomical unit still used today?
Used internationally in astronomy for solar-system-scale distances.