How to Convert Miles to Nautical miles (mi 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 miles into nautical miles by hand, with examples and a quick-reference table.
The conversion
To convert miles to nautical miles, multiply the value by 0.8689762419. To go the other way, divide by the same number (or multiply by 1.150779448). For a quick estimate, multiply by about 0.87.
Nautical miles = miles × 0.8689762419
Worked examples
- 3 mi = 2.6069 nmi
- 12.5 mi = 10.8622 nmi
- 75 mi = 65.1732 nmi
Miles to Nautical miles table
| Miles | Nautical miles |
|---|---|
| 1 mi | 0.868976 nmi |
| 2 mi | 1.738 nmi |
| 5 mi | 4.3449 nmi |
| 10 mi | 8.6898 nmi |
| 20 mi | 17.3795 nmi |
| 25 mi | 21.7244 nmi |
| 50 mi | 43.4488 nmi |
| 100 mi | 86.8976 nmi |
| 250 mi | 217.2441 nmi |
| 500 mi | 434.4881 nmi |
| 1,000 mi | 868.9762 nmi |
Common questions
Is mi 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 Miles converter.
Mistakes to avoid
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
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.
Background
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
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.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For any value, use the Miles to Nautical miles Converter or browse all length converters.
Run your own numbers: Miles to Nautical miles Converter