County Maps US

Tools Distance, area and drive time

Bearing and Compass Calculator

Four bearings are given because they differ: the great-circle heading changes as you travel, the rhumb line does not, and a compass needle points at magnetic north.

How to use it

  1. Enter the start point and the destination as addresses, cities or coordinates.
  2. Press Calculate bearing.
  3. Read the true bearings, the magnetic bearing for a hand compass, and the declination used. The compass rose shows true north, magnetic north and the bearing; the map shows the great circle and the rhumb line.

How it works

Initial and final great-circle bearings and the rhumb-line (constant heading) bearing are computed in the browser from the two coordinates on a sphere. The map draws the great circle as a curve and the rhumb line as a straight line, which on this Mercator map it is.

Magnetic declination at the start point, for today, comes from the World Magnetic Model 2025 (NCEI and the British Geological Survey, epoch 2025.0, degree 12), evaluated entirely in the browser and checked against the published WMM2025 test values. Magnetic bearing is true bearing minus declination. The model gives the main field only; local iron, power lines and magnetic rock can move a compass by more, and near the magnetic poles a compass is unreliable, which the tool flags.

Questions

What is the difference between a true and a magnetic bearing?
A true bearing is measured from true north, the direction to the geographic pole, which maps and GPS use. A magnetic bearing is measured from where a compass needle points. The difference is the magnetic declination, which varies by place and slowly with time.
Which bearing do I set on my compass?
The magnetic bearing at the start. If you are walking a long way, the direction to hold changes a little as declination changes along the route, and for a great circle the true heading itself changes.
What is a rhumb line?
A path of constant compass heading. It is slightly longer than the great circle but you never have to change course, which is why ships and small aircraft use it for short legs.
How accurate is the declination?
The World Magnetic Model is typically within a degree of the true value away from the poles; local anomalies can add more. It is the same model that phones and GPS receivers use.

All map tools, free and without an account. Location data is processed in your browser and by the open geocoding services named on the sources page; nothing is stored by this site.