Fathoms to Nautical Miles
Convert fathoms to nautical miles instantly — one fathom is 0.000987473 nautical miles.
| Fathoms | Nautical Miles |
|---|---|
| 1 ftm | 0.000987 nmi |
| 2 ftm | 0.001975 nmi |
| 3 ftm | 0.002962 nmi |
| 5 ftm | 0.004937 nmi |
| 10 ftm | 0.009875 nmi |
| 25 ftm | 0.024687 nmi |
| 50 ftm | 0.049374 nmi |
| 100 ftm | 0.098747 nmi |
How to use
- Enter a value in the Fathoms field.
- The Nautical Miles figure appears immediately — no button to press.
- Typing in the Nautical Miles field converts back to Fathoms the same way.
- Use the reference table for the values that come up most often.
Fathoms to Nautical Miles formula
The factor from fathoms to nautical miles is 0.000987473002.
nmi = ftm × 0.000987473002
Why this factor: the fathom and the nautical mile are both defined against the meter, so dividing one definition by the other gives 0.000987473002 directly. Both definitions are set out in full below.
To go the other way, divide by 0.000987473002 — or use the Nautical Miles to Fathoms converter, which is the same calculation reversed.
Worked example
Start with 5 ftm. Multiply by 0.000987473002 to get 0.004937 nmi.
5 ftm × 0.000987473002 = 0.004937 nmi
The converter above does this for any value you type, in either direction.
What is a fathom?
A fathom is six feet, the traditional unit for water depth.
Definition: Six international feet, so exactly 1.8288 meters.
Where it is used: Nautical charts, depth soundings, and anchor and cable lengths.
What is a nautical mile?
A nautical mile is the distance unit of sea and air navigation, chosen so it tracks latitude on a chart.
Definition: Exactly 1,852 meters, fixed by the 1929 International Extraordinary Hydrographic Conference. It approximates one arcminute of latitude.
Where it is used: Marine and aviation navigation, maritime boundaries, and the basis of the knot (one nautical mile per hour).
Worth knowing: About 15% longer than a statute mile — mixing the two is a classic navigation error.
Fathoms vs Nautical Miles
The fathom and the nautical mile belong to the same family of units, so converting between them is usually a matter of shifting a decimal point or applying a small whole-number factor.
Frequently asked questions
How many nautical miles are in a fathom?
One fathom equals 0.000987473002 nautical miles.
What is the formula to convert fathoms to nautical miles?
Multiply the number of fathoms by 0.000987473002. To reverse it, divide by 0.000987473002 instead.
How do I convert nautical miles back to fathoms?
Divide by 0.000987473002, which is the same as multiplying by 1012.68591.
How many nautical miles are in 10 fathoms?
10 ftm works out to 0.009875 nmi.
Is there anything to watch out for with nautical miles?
About 15% longer than a statute mile — mixing the two is a classic navigation error.
How is the fathom defined?
Six international feet, so exactly 1.8288 meters.