What is a nautical mile?

An international nautical mile (NM) is exactly 1,852 meters (1.852 km), according to the NIST conversion factor. Its navigation use is historically tied to angular measurement on the Earth.

What is the Haversine formula?

The Haversine formula calculates the great-circle distance between two points on a sphere given their latitudes and longitudes. It accounts for Earth's curvature and is accurate to within 0.3% for most practical distances.

Is this the same as rhumb-line distance?

No. This tool computes the great-circle (orthodrome) distance, which is the shortest path over the Earth's surface. A rhumb line (loxodrome) follows a constant compass bearing and is generally longer except along meridians or the equator.

How accurate is the result?

The calculation uses a spherical mean-Earth radius, so it can differ from an ellipsoidal geodesic. More importantly for marine use, it does not route around land, hazards or regulations. Use appropriate charts and navigation systems for passage planning.

Is this an actual sea-route distance?

No. It is the shortest spherical surface arc between the two coordinates and may cross land or unsafe water. Actual voyage distance depends on waypoints, coastlines, traffic schemes, weather and operating restrictions.

What coordinate format should I use?

Enter decimal degrees (e.g., -33.8688 for south). Positive values are North/East, negative are South/West. Latitude ranges from -90 to 90, longitude from -180 to 180.

What does the bearing represent?

The initial bearing is the compass heading (0–360°) you would follow from the origin to reach the destination along the great-circle route. Due to Earth's curvature this heading changes as you travel, unlike a rhumb line.

Nautical Distance Calculator

Enter two coordinates for spherical great-circle distance, initial/reverse bearings and optional underway time at a chosen speed. This is not a navigable sea route and does not avoid land or hazards.

Origin

Latitude

Longitude

Decimal degrees. Positive = N/E, negative = S/W.

Destination

Latitude

Longitude

Quick presets:

Optional constant speed (knots)

Produces ideal underway time only; excludes stops, currents, weather and route detours.

Enter coordinates or choose a preset, then click Calculate.

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Summary

Enter two coordinates for spherical great-circle distance, initial/reverse bearings and optional underway time at a chosen speed. This is not a navigable sea route and does not avoid land or hazards.

How it works

Enter the latitude and longitude of your starting point (Origin).
Enter the latitude and longitude of your destination point.
Enter each coordinate in signed decimal degrees (for example, 40.7128).
The tool applies the Haversine formula to compute the great-circle distance.
Results appear instantly in nautical miles, kilometers, and statute miles.
The initial bearing (compass heading) from origin to destination is also shown.

Use cases

Screen coordinate-to-coordinate distance and ideal underway time.
Calculate flight distances for aviation route planning.
Compare geometric legs before chart-based route planning.
Verify chart plotter readings with an independent calculation.
Estimate fuel requirements for marine or aerial journeys.
Cross-reference GPS coordinates in navigation training exercises.
Compare distances for search-and-rescue planning.
Compute leg distances for a multi-waypoint passage plan.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu