Convert length and distance units — meters, feet, inches, kilometers, miles, light years and more.
| Unit | Name | Value |
|---|---|---|
| 0.001 au | 8.18023e+07 ftm | |
| 0.01 au | 8.18023e+08 ftm | |
| 0.1 au | 8.18023e+09 ftm | |
| 1 au | 8.18023e+10 ftm | |
| 5 au | 4.09011e+11 ftm | |
| 10 au | 8.18023e+11 ftm | |
| 50 au | 4.09011e+12 ftm | |
| 100 au | 8.18023e+12 ftm | |
| 1000 au | 8.18023e+13 ftm |
Multiply the number of Astronomical Units by 81802300000 to get Fathoms. Formula: ftm = au × 81802300000. Example: 10 au × 81802300000 = 818023000000 ftm. To reverse, divide Fathoms by 81802300000 to get Astronomical Units.
| Astronomical Unit (au) | Fathom (ftm) |
|---|---|
| 0.001 au | 81802300 ftm |
| 0.01 au | 818023000 ftm |
| 0.1 au | 8180230000 ftm |
| 0.5 au | 40901100000 ftm |
| 1 au | 81802300000 ftm |
| 2 au | 163605000000 ftm |
| 5 au | 409011000000 ftm |
| 10 au | 818023000000 ftm |
| 20 au | 1.636×1012 ftm |
| 50 au | 4.0901×1012 ftm |
| 100 au | 8.1802×1012 ftm |
| 250 au | 2.0451×1013 ftm |
| 500 au | 4.0901×1013 ftm |
| 1000 au | 8.1802×1013 ftm |
| 10000 au | 8.1802×1014 ftm |
To convert Astronomical Unit to Fathom, multiply by 81802300000. Example: 10 au = 818023000000 ftm
To convert Fathom back to Astronomical Unit, divide by 81802300000 (multiply by 1.2225×10-11). Use the swap button above.
Start with 100 Astronomical Units = 8.1802×1012 ftm as your reference point. Scale up or down from there.
Maritime educators teaching celestial navigation bridge fathoms — the traditional nautical depth unit — with astronomical units used in celestial mechanics, helping students appreciate the scale from ocean depth to solar system.
1 AU = 81.8 billion fathoms. This extraordinary number is used in science communication to make astronomical distances viscerally understandable — expressing Earth-Sun distance in a unit sailors once used to measure harbour depth.
Authors writing about the history of measurement compare the fathom — used by ancient mariners — with the astronomical unit, formalised centuries later, to illustrate how human measurement systems evolved with our exploration ambitions.
Interdisciplinary researchers studying ocean worlds (Europa, Enceladus) express ocean depths in fathoms for oceanographic context while orbital distances use AU — conversion needed when writing cross-disciplinary papers.
Science communicators use AU-to-fathom conversions in public outreach to make astronomical distances tangible: "The distance to the Sun, measured in the same units sailors used to chart the ocean floor..."
Complete length conversion databases include AU-to-fathom for historical completeness and to serve researchers working with legacy nautical records or cross-referencing historical astronomical observations.
The Astronomical Unit is a unit of Length measurement (symbol: au). 1 au = 81802300000 ftm. Used in scientific and practical Length measurement applications.
The Fathom is a unit of Length measurement (symbol: ftm). It is part of an internationally recognised measurement system used alongside the Astronomical Unit.
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 to measure it precisely. 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.
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. Samuel Pepys referenced fathoms in 17th-century naval logs. 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.
Common use: Astronomical Unit to Fathom conversion is needed when working with international standards, scientific publications, or reference materials that use different unit systems for Length measurement.