How to Convert Feet to Nautical miles (ft to nmi)
Length conversions come up when reading overseas furniture specs, cycling the Round Island Route in kilometres while a foreign app shows miles, or checking marine distances in the Singapore Strait in nautical miles. This guide shows how to convert feet into nautical miles by hand, with examples and a quick-reference table.
The conversion
To convert feet to nautical miles, multiply the value by 0.0001645788. To go the other way, divide by the same number (or multiply by 6,076.1154855643). Because the factor is tiny, scientific notation keeps the numbers manageable.
Nautical miles = feet × 0.0001645788
Worked examples
- 3 ft = 0.000494 nmi
- 12.5 ft = 0.002057 nmi
- 75 ft = 0.012343 nmi
Feet to Nautical miles table
| Feet | Nautical miles |
|---|---|
| 1 ft | 0.000165 nmi |
| 2 ft | 0.000329 nmi |
| 5 ft | 0.000823 nmi |
| 10 ft | 0.001646 nmi |
| 20 ft | 0.003292 nmi |
| 25 ft | 0.004114 nmi |
| 50 ft | 0.008229 nmi |
| 100 ft | 0.016458 nmi |
| 250 ft | 0.041145 nmi |
| 500 ft | 0.082289 nmi |
| 1,000 ft | 0.164579 nmi |
Common questions
Is ft to nmi exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Nautical miles to Feet converter.
Mistakes to avoid
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Background
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
For any value, use the Feet to Nautical miles Converter or browse all length converters.
Run your own numbers: Feet to Nautical miles Converter