What Are Nautical Miles? Why Boats & Planes Use Them Instead of Regular Miles
Distance on the road is measured in miles, but once you get on the water or in the air, the units change. Whether you're planning a boat rental, reading a marine chart, checking a GPS, or estimating how long it'll take to reach a sandbar, fishing spot, or waterfront restaurant, understanding what are nautical miles and knots makes the whole experience easier.
In this article, you'll learn:
What a nautical mile is
How nautical miles compare to regular miles
What knots mean and how they relate to speed
Why boats and planes use nautical miles instead of regular miles
How everyday boaters can use this information when out on the water
What Is a Nautical Mile?
A nautical mile is a unit of distance used for travel on water and in the air. One nautical mile equals 1.1508 regular miles, or 1,852 meters. NOAA explains that nautical miles are based on the Earth's latitude and longitude system, with one nautical mile equal to one minute of latitude.
A regular mile is mostly useful for roads. A nautical mile is useful for navigation over the curved surface of the Earth. Marine charts, aviation charts, GPS systems, and navigation routes all use nautical miles as the standard unit of distance.
Nautical Mile vs. Regular Mile
Understanding nautical miles vs miles comes down to one key difference: one is built for roads, the other is built for the globe.
| Boat Speed | Approx. MPH |
|---|---|
| 5 knots | 5.8 mph |
| 10 knots | 11.5 mph |
| 20 knots | 23 mph |
| 30 knots | 34.5 mph |
Why Is a Nautical Mile Longer Than a Regular Mile?
A regular mile (also called a statute mile) is 5,280 feet. The international nautical mile is about 6,076 feet. BoatUS notes that this difference is large enough to matter when setting up GPS units or reading navigation information.1
The reason comes down to how the nautical mile was defined:
The Earth is divided into degrees of latitude
Each degree has 60 minutes
One minute of latitude is approximately one nautical mile
That direct relationship between Earth's coordinate grid and this unit of measurement is what makes the nautical mile so reliable for navigation at sea or in the air.
Easy Example
If your GPS says a destination is 10 nautical miles away, that's about 11.5 regular miles
If your boat is traveling at 20 knots, it's moving 20 nautical miles per hour, which is about 23 mph
Any time you need to convert nautical miles to miles, just multiply by 1.1508, so for example, 10 nautical miles works out to about 11.5 regular miles. These are two different measurements. Planning your arrival time, fuel range, or return window using the wrong unit will give you incorrect numbers.
What Are Knots, and How Are They Related to Nautical Miles?
A knot is a speed measurement. NIST defines a knot as one nautical mile per hour, or 1,852 meters per hour.
One thing to avoid: saying "20 knots per hour." Since knots already means nautical miles per hour, adding "per hour" doubles up on the unit. The correct usage is simply 20 knots.
Knots vs. MPH
| Boat Speed | Approx. MPH |
|---|---|
| 5 knots | 5.8 mph |
| 10 knots | 11.5 mph |
| 20 knots | 23 mph |
| 30 knots | 34.5 mph |
Why Do Boats Use Nautical Miles Instead of Regular Miles?
Marine navigation depends on charts, coordinates, waypoints, channels, buoys, and distances over water, not street signs. Marine charts and navigation systems use nautical miles because they connect directly to latitude and longitude. Using statute miles at sea adds an unnecessary conversion step and opens you up to errors when reading marine charts. Since everything is already displayed in nautical miles, stick with that.
For some tips on preparing before you head out, check out Your Boat Club's boat trip planning tips for a perfect getaway.
Nautical Miles Help Boaters Estimate Time
For most boaters, the biggest practical advantage of understanding nautical miles is estimating travel time. The formula is simple:
Time = Distance ÷ Speed
Example:
Destination: 12 nautical miles away
Boat speed: 20 knots
Estimated travel time: 12 ÷ 20 = 0.6 hours, or about 36 minutes
Real boating time will always be longer. Account for no-wake zones, wind, current, waves, boat traffic, docking time, fuel stops, and local speed rules. Build in a buffer, especially if you're on a rental with a set return time.
Nautical Miles Help with Route Planning
Knowing your distances in nautical miles helps you plan smarter trips:
Distance to the next marina: How far can you go before you need fuel?
Distance to an island or sandbar: Know the realistic travel time before you go
Fuel planning: Cross-reference your range against your destination distance
Return-trip timing: Work backward from when you need to be back at the dock
Emergency communications: Accurately relay your position if needed
GPS and chartplotter settings: Confirm you're using the correct unit before you leave
For more on staying safe on the water, read Your Boat Club's guide on boating safety in choppy water.
Why Do Planes Use Nautical Miles Too?
If you've ever wondered why do boats and planes use nautical miles instead of regular miles, the answer is the same for both: they navigate by coordinates, not roads.
Aviation routes cross large distances over the curved surface of the Earth, and pilots navigate with coordinates, waypoints, airways, and charts – all of which rely on the same latitude and longitude framework. The FAA's air traffic publications state that "miles" generally means nautical miles unless otherwise specified, with statute miles reserved for visibility measurements.2
Same Logic, Different Environment
Boats navigate across water
Planes navigate through airspace
Both need a distance system that works with latitude and longitude
Both use knots for speed and nautical miles for distance
Regular miles are still useful on land. But nautical miles are better suited for navigation where there are no roads.
What Nautical Miles Mean for Everyday Boaters
1. Check Your GPS Settings
Before you leave the dock, confirm what unit your GPS is displaying. Many GPS systems and smartphone apps let you toggle between statute miles, nautical miles, and kilometers. BoatUS specifically warns that confusing statute miles and nautical miles can matter because a statute mile is about 12% shorter, which is enough to skew both your distance readings and your time estimates.1
Not sure what else to check before heading out? Read Your Boat Club's guide on whether you need a license to rent a boat to learn what every renter should know.
2. Don't Plan a Boat Trip Like a Road Trip
A destination that looks "10 miles away" on land may not translate to a 10-mile boat route. Water routes depend on marked channels, no-wake zones, shallow areas, bridges, locks, and local rules that don't show up on a standard map.
3. Ask Local Staff for Realistic Timing
Don't overlook one of the best free resources available to boaters: local marina staff. Your Boat Club staff can walk you through expected travel times to common destinations, clarify local regulations, and set expectations for conditions once you leave the dock. Whether you're on a day rental or exploring a Your Boat Club membership, that local knowledge makes a real difference.
4. Use Nautical Miles for Planning, but Keep It Simple
For most casual boaters, the goal isn't to become a navigator overnight. It's to understand enough to read the basics, ask better questions, and plan a safer, smoother day on the water. Know that a nautical mile is longer than a regular mile, and that knots measure speed in nautical miles per hour, and you're already ahead of most beginners. So the next time someone on the dock asks you what are nautical miles, you'll have a solid answer and a safer, better-planned trip to show for it.
Learn Boating Basics with Your Boat Club
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FAQs About Nautical Miles
How many regular miles are in one nautical mile?
One nautical mile equals about 1.1508 regular miles.
How many feet are in a nautical mile?
One international nautical mile equals about 6,076 feet.
Is a knot the same as a nautical mile?
No. A nautical mile measures distance. A knot measures speed. One knot means traveling one nautical mile per hour.
Do lake boaters need to know nautical miles?
Yes, at least at a basic level. Even on lakes, GPS units, marine apps, route distances, and boat speeds may use nautical miles and knots as default settings.
Should beginner boaters memorize conversions?
No. Know the basics: one nautical mile is longer than one regular mile, and one knot equals one nautical mile per hour. Everything else can be looked up as needed.
Sources:
Boat Owners Association of The United States. “What 222,000 Boaters Got Wrong.” BoatUS News Room, https://www.boatus.com/news-room/release/what-222000-boaters-got-wrong, Jan. 10, 2024. Accessed July 21, 2026
Federal Aviation Administration. “Section 2: Terms of Reference.” FAA Order JO 7110.10EE — Flight Services, Chapter 1, https://www.faa.gov/air_traffic/publications/atpubs/fs_html/chap1_section_2.html, effective July 9, 2026. Accessed July 21, 2026
