A nautical mile is exactly 1,852 meters.
Nautical miles to Astronomical units Converter — nmi to AU
Convert Nautical mile (nmi) to Astronomical unit (AU) using the exact conversion factor (1 nautical mile = 1.237986e-8 astronomical unit). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Nautical miles to Astronomical units converter
Converter
Length Converter
Convert SI, imperial, US customary, astronomical, scientific, and historical length units.
Context values
Some unit families need one extra value for a physically accurate result.
An astronomical unit is the mean Earth-Sun distance.
Result = input x 1852 / 1.49597871e+11.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Nautical miles to Astronomical units
Nautical mile and Astronomical unit both measure length. Nautical mile is typically associated with used internationally in maritime navigation and aviation., while Astronomical unit is typically associated with used internationally in astronomy for solar-system-scale distances..
Formula
astronomical units = nautical miles × 1.237986e-8
This factor comes from each unit's defined relationship to the category's base unit: 1 nautical mile equals 1852 base units, and 1 astronomical unit equals 149597870700 base units, so dividing one by the other gives the direct nautical mile-to-astronomical unit factor of 1.237986e-8.
Simple example
1 nmi × 1.237986e-8 = 1.237986e-8 AU
1 nautical mile = 1.237986e-8 astronomical units.
Real-world example
10 nmi × 1.237986e-8 = 1.237986e-7 AU
10 nautical miles = 1.237986e-7 astronomical units.
Conversion table
| Nautical mile (nmi) | Astronomical unit (AU) |
|---|---|
| 1 nmi | 1.237986e-8 AU |
| 5 nmi | 6.189928e-8 AU |
| 10 nmi | 1.237986e-7 AU |
| 21.0975 nmi | 2.61184e-7 AU |
| 42.195 nmi | 5.22368e-7 AU |
| 100 nmi | 0.000001238 AU |
Reverse conversion: Astronomical unit to Nautical mile
1.237986e-8 AU × 80776388.07 = 1.000000376 nmi
1.237986e-8 astronomical units = 1.000000376 nautical miles.
nautical miles = astronomical units × 80776388.067
For a page dedicated to this direction, see Astronomical unit to Nautical mile.
Nautical mile vs. Astronomical unit
| Aspect | Nautical mile | Astronomical unit |
|---|---|---|
| Family | Non-SI unit accepted for use with SI (maritime/aviation) | Non-SI unit accepted for use with SI (astronomical) |
| Typical use | Marine and aviation distance and navigation | Measuring distances within the solar system (planetary orbits) |
| Where it's used | Used internationally in maritime navigation and aviation. | Used internationally in astronomy for solar-system-scale distances. |
Understanding the Nautical mile
Nautical mile (nmi) measures distance. The international nautical mile is defined as exactly 1,852 meters, standardized in 1929. It is classified as a Non-SI unit accepted for use with SI (maritime/aviation).
Where it's used: Used internationally in maritime navigation and aviation.
Uses of the Nautical mile today
- Marine and aviation distance and navigation
- Basis for the knot (nautical miles per hour)
History of the Nautical mile
The nautical mile was historically defined as one minute of latitude along a meridian, directly tying sea navigation to the Earth's geometry, which made it practical for chart-based navigation using a ship's known latitude. The International Hydrographic Bureau standardized it at exactly 1,852 meters in 1929, a value close to the traditional latitude-based definitions used by different countries.
Historical origin. Nautical mile was not the invention of a single named person; it developed through the process described above.
Understanding the Astronomical unit
Astronomical unit (AU) measures distance. The astronomical unit is defined as exactly 149,597,870,700 meters, close to the average Earth-Sun distance. It is classified as a Non-SI unit accepted for use with SI (astronomical).
Where it's used: Used internationally in astronomy for solar-system-scale distances.
Uses of the Astronomical unit today
- Measuring distances within the solar system (planetary orbits)
- Astronomical calculations and spacecraft navigation
- Popular science communication about the solar system
History of the Astronomical unit
The astronomical unit originated from 17th-19th century attempts to measure the Earth-Sun distance, refined over time using transits of Venus and later radar and spacecraft ranging.
In 2012, the International Astronomical Union fixed the AU at exactly 149,597,870,700 meters, replacing its earlier definition (tied to gravitational calculations) with a simple fixed distance, independent of the slightly-variable actual Earth-Sun distance.
Historical origin. Astronomical unit was not the invention of a single named person; it developed through the process described above.
Nautical mile — sources
- BIPM SI Brochure — Non-SI units accepted for use with SI — Lists the nautical mile among accepted non-SI units.
Astronomical unit — sources
- IAU Resolution B2 (2012) — Fixes the astronomical unit at exactly 149,597,870,700 meters.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many astronomical units are in 1 nautical mile?
1 nautical mile equals 1.237986e-8 astronomical units, using the exact defined conversion factor rather than an estimate.
How do I convert nautical mile to astronomical unit?
Multiply the nautical mile value by 1.237986e-8. The converter above does this instantly to whatever precision you set.
How do I convert astronomical unit back to nautical mile?
Use the reverse factor: 1 astronomical unit equals 80,776,388.07 nautical miles. You can also use the swap control in the converter above to flip the direction instantly.
What is a nautical mile?
Nautical mile (nmi) measures distance. The international nautical mile is defined as exactly 1,852 meters, standardized in 1929. It is classified as a Non-SI unit accepted for use with SI (maritime/aviation).
What is a astronomical unit?
Astronomical unit (AU) measures distance. The astronomical unit is defined as exactly 149,597,870,700 meters, close to the average Earth-Sun distance. It is classified as a Non-SI unit accepted for use with SI (astronomical).
Is the nautical mile to astronomical unit conversion exact?
Yes. The astronomical unit is defined as exactly 149,597,870,700 meters, close to the average Earth-Sun distance. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Where is the nautical mile still used today?
Used internationally in maritime navigation and aviation.