Convert length and distance units — meters, feet, inches, kilometers, miles, light years and more.
| Unit | Name | Value |
|---|---|---|
| 0.001 ftm | 1.222e-14 au | |
| 0.01 ftm | 1.222e-13 au | |
| 0.1 ftm | 1.222e-12 au | |
| 1 ftm | 1.222e-11 au | |
| 5 ftm | 6.112e-11 au | |
| 10 ftm | 1.222e-10 au | |
| 50 ftm | 6.112e-10 au | |
| 100 ftm | 1.22246e-09 au | |
| 1000 ftm | 1.22246e-08 au |
Multiply the number of Fathoms by 1.2225×10-11 to get Astronomical Units. Formula: au = ftm × 1.2225×10-11. Example: 10 ftm × 1.2225×10-11 = 1.2225×10-10 au. To reverse, divide Astronomical Units by 1.2225×10-11 to get Fathoms.
| Fathom (ftm) | Astronomical Unit (au) |
|---|---|
| 0.001 ftm | 1.2225×10-14 au |
| 0.01 ftm | 1.2225×10-13 au |
| 0.1 ftm | 1.2225×10-12 au |
| 0.5 ftm | 6.1123×10-12 au |
| 1 ftm | 1.2225×10-11 au |
| 2 ftm | 2.4449×10-11 au |
| 5 ftm | 6.1123×10-11 au |
| 10 ftm | 1.2225×10-10 au |
| 20 ftm | 2.4449×10-10 au |
| 50 ftm | 6.1123×10-10 au |
| 100 ftm | 1.2225×10-9 au |
| 250 ftm | 3.0561×10-9 au |
| 500 ftm | 6.1123×10-9 au |
| 1000 ftm | 1.2225×10-8 au |
| 10000 ftm | 1.22246e-07 au |
To convert Fathom to Astronomical Unit, multiply by 1.2225×10-11. Example: 10 ftm = 1.2225×10-10 au
To convert Astronomical Unit back to Fathom, divide by 1.2225×10-11 (multiply by 81802300000). Use the swap button above.
Start with 100 Fathoms = 1.2225×10-9 au as your reference point. Scale up or down from there.
Navigation instructors bridging celestial navigation (AU for solar system distances) and maritime navigation (fathoms for sea depth) use fathom-to-AU conversion to illustrate the full scale of human measurement systems.
Researchers studying subsurface oceans on Europa and Enceladus describe ocean depths in fathoms for comparison with Earth's oceans, while expressing the moon's orbital distance in AU — cross-scale conversion needed.
1 AU = 81.8 billion fathoms. Science communicators use this to make astronomical distances tangible for maritime audiences: the Earth-Sun distance expressed in the same unit used to measure ocean depth.
The fathom was the unit of ocean exploration for 500 years. Comparing it to the AU — the unit of space exploration — illustrates how human measurement expanded from ocean depths to solar system distances.
Satellites monitoring both ocean depth (in fathoms from sonar altimetry) and orbital altitude (in AU from Earth) require cross-scale unit conversion in multi-purpose earth observation system documentation.
Planetarium educators use fathom-to-AU comparisons to connect the ocean-going heritage of their coastal audiences with the scale of astronomical distances — making space science personally relevant.
The Fathom is a unit of Length measurement (symbol: ftm). 1 ftm = 1.2225×10-11 au. Used in scientific and practical Length measurement applications.
The Astronomical Unit is a unit of Length measurement (symbol: au). It is part of an internationally recognised measurement system used alongside the Fathom.
The fathom derives from the Old English 'fæthm', meaning the span of outstretched arms — roughly 6 feet or 1.8 metres. It was the primary depth measurement unit used by mariners for millennia, recorded in the Bible and used by ancient Greeks. The word 'fathom' also entered English as a verb meaning to understand something deeply — from the idea of plumbing the depths. Despite metrication, fathoms remain on admiralty charts and in nautical tradition worldwide.
The astronomical unit has ancient roots — Aristarchus of Samos attempted to measure the Earth-Sun distance around 270 BC, estimating it at 18–20 lunar distances (the true value is about 390). For centuries the AU was estimated using Venus transit observations and trigonometry. Edmond Halley organised the first coordinated international transit-of-Venus expedition in 1716. The modern value was determined by radar ranging to Venus in 1961. The IAU formally defined the AU as exactly 149,597,870,700 metres in 2012 — a fixed constant of physics, not a measured distance.
Common use: Fathom to Astronomical Unit conversion is needed when working with international standards, scientific publications, or reference materials that use different unit systems for Length measurement.