Sailing Compass & Bearing Compass: Magnetic North vs True North
A clear guide for sailors and race officials on how a sailing compass (bearing compass) works, the difference between Magnetic North and True North, and when to use each on the water.
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Sailing compass Bearing compass Magnetic vs True
Does a bearing compass show True North?
No. A sailing compass or handheld bearing compass shows Magnetic North, not True North.
Magnetic North vs True North
Magnetic North
The direction the compass needle points, following Earth’s magnetic field. Immediate, battery-free, and perfect for quick bearings.
True North
The geographic North Pole. Nautical charts and plotted courses are referenced to True North.
Because charts are aligned to True, you convert your magnetic readings before plotting.
The Two Corrections You Need
- Variation (Declination) — The difference between Magnetic and True at your location (printed on charts; changes by area and time).
- Deviation — Local magnetic errors from metals/electronics aboard your vessel; determined by a deviation card/swing.
Core formula: True = Magnetic + Variation + Deviation
Rule of thumb: East is least to worry about because you simply add; more precisely — East = Add, West = Subtract.
Quick Magnetic → True Examples
| Compass Reading (Magnetic) | Variation | Deviation | True Bearing |
|---|---|---|---|
| 045° | +7°E | 0° | 052° (True) |
| 120° | −5°W | +2° | 117° (True) |
| 270° | +3°E | −1° | 272° (True) |
Why Sailors Still Use Magnetic
- Simplicity at sea — Instant direction, no power or satellites.
- Direct bearings — A bearing compass measures right away against Magnetic North.
- Clear communication — Crews often speak in magnetic bearings on the water.
- Small differences — In many regions, variation is only a few degrees (still correct for plotting).
- Reliable backup — If electronics fail, the magnetic compass keeps you safe.
Best Practice on the Water
Chartwork & plotting → Convert to True North (apply variation + deviation).
Real-time maneuvering → Use Magnetic North for quick course checks and bearings.
Recommended Gear
For reliable bearings in all conditions, explore the Windie Bearing Compass — built for sailors and race officials, water-ready, and easy to use one-handed.