# Fathoms to Astronomical Units (ftm to au)

Source: https://www.unitconvertercalculator.com/length/fathoms-to-astronomical-units/

**1 ftm = 1.2224772929205E-11 au**

One fathom equals approximately 1.222 x 10-11 astronomical units. The deepest ocean trench (about 6,000 fathoms) is only 7.3 x 10-8 AU below sea level. The fathom measures maritime depth; the AU measures the Earth-Sun distance. No oceanographer has ever expressed depth in AU.

## Formula

Convert Fathoms to Astronomical Units

## Conversion Table

| Fathoms (ftm) | Astronomical Units (au) |
|---|---|
| 1 ftm | 1.222477292E-11 au |
| 10 ftm | 1.2224772929E-10 au |
| 100 ftm | 1.22247729292E-9 au |
| 1000 ftm | 1.22247729292E-8 au |
| 10000 ftm | 1.2224772929204E-7 au |
| 100000 ftm | 1.2224772929204E-6 au |
| 1000000 ftm | 1.2224772929205E-5 au |
| 10000000 ftm | 0.00012224772929205 au |
| 100000000 ftm | 0.0012224772929205 au |

## Units

### Fathom (ftm)

Exactly 6 feet (1.8288 m). Traditionally used to measure water depth in nautical contexts. Originally based on the span of outstretched arms.

### Astronomical Unit (au)

Exactly 149,597,870,700 meters by IAU 2012 definition. Roughly the average distance from the Earth to the Sun. Used for distances within our solar system.

## Background

The Earth-Sun distance (1 AU) would be about 81.8 billion fathoms of water depth if such a thing existed. The Mariana Trench at 6,011 fathoms is barely 0.0000073% of an AU. These numbers show how the entire ocean is a thin film on the astronomical scale.

## Good to Know

The entire depth of the ocean from surface to trench bottom is only 0.0000073% of the Earth-Sun distance. If the AU were a football field, the ocean would be thinner than a sheet of paper laid on the goal line.

## FAQ

### How many AU is 1 fathom?

One fathom equals approximately 1.222 x 10-11 AU. A fathom is about 12 trillionths of an AU.

### How many fathoms are in 1 AU?

One AU contains approximately 8.181 x 1010 fathoms (about 81.8 billion fathoms).

### Is this conversion useful?

No. Fathoms measure ocean depths from 0 to about 6,000. AU measures planetary distances. The entire ocean depth is an infinitesimal fraction of 1 AU.

## Non-Frequently Asked Questions

### How deep would the ocean need to be to reach the Sun?

The Sun is 1 AU = about 8.178 x 1010 fathoms away. The actual ocean is only about 6,000 fathoms deep at its maximum. You would need to stack about 13.6 million Mariana Trenches to reach the Sun. The ocean is deep but not that deep.

### If the Mariana Trench were 1 AU deep, how long would a submarine take to reach the bottom?

At a typical submarine descent rate of about 5 fathoms per minute, reaching 8.178 x 1010 fathoms would take about 31 million years. Pack a very large lunch.

### Is the fathom the most dramatic unit for expressing astronomical distances?

Saying 'the Sun is 82 billion fathoms away' does sound more ominous than '1 AU.' But astronomers prefer compact numbers. Nobody writes scientific papers in fathoms. The drama is not worth the extra zeros.

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## See Also

- [Astronomical Units to Fathoms](https://www.unitconvertercalculator.com/length/astronomical-units-to-fathoms/)