Best Boat Compasses: Steering and Handheld Picks

GPS tells you where you are and the direction you are moving over the ground, but a magnetic compass tells you which way the boat is pointing right now. Steering a compass course is steadier than chasing a plotter's course-over-ground arrow, which lags behind the boat's motion. A magnetic compass also keeps working when batteries are flat, a breaker trips or electronics get wet.

Ritchie makes the point that GPS failure requires dead reckoning, the technique of estimating position from heading, speed and time. That only works with a reliable heading source.

The bigger the card, the further away you can read it. Plastimo sizes its compasses to boat length: the Offshore 75 has a 70 mm conical card graduated every 5° and is listed for boats of 5–8 metres (17–26 ft), while the Offshore 135 is aimed at boats over 9 metres. On a sailboat, think about where the helmsman sits when heeled; you may be reading the compass from the high side, much further away than at the dock.

A direct-read card, like the Ritchie Explorer's, shows the heading at the back of the card, on the side away from you, so you read it looking forward. A front-read or flat card shows numbers on the side facing you with a lubber line (the fixed mark that shows the boat's heading). Both work; what matters is that the card is easy for your helmsman to read at a glance, day and night.

A sailboat may sail for hours heeled 15–25°. The compass card must stay level and free to turn at that angle, otherwise it sticks or reads inaccurately. Some compasses use internal gimbals or a deep bowl to cope with heel; many compact powerboat compasses are designed for flatter running. Check the manufacturer's heel specification for the exact model.

Common mounting styles are binnacle (on the steering pedestal), bulkhead (flush into a cockpit bulkhead, often in pairs so one is visible from each side) and bracket (on a surface with a removable bracket). Mount the compass on the boat's centreline or parallel to it so the lubber line is aligned with the keel.

Deviation is the error caused by magnetic material and electrical currents aboard: engines, speakers, wiring, handheld radios and even a can of drink near the compass. Many compasses, including the Ritchie Explorer, include built-in compensators (small adjustable magnets) to reduce it.

After installing, swing the compass: compare its readings with known bearings or GPS headings in calm water on several headings, adjust the compensators, and record any remaining errors on a deviation card. Keep speakers and phones away from it, and recheck after adding electronics.

A hand-bearing compass lets you take bearings of landmarks or other vessels to plot your position or check collision risk: if another vessel's bearing stays constant while the range closes, risk of collision exists. Some compasses, such as the Plastimo Iris 100, include sighting vanes and a removable mount, so they serve as both a small boat's steering compass and a hand-bearing compass.

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Budget tiers and the decision that matters

Small sailboats: a gimballed compact like the Iris 100 gives you both a steering compass and a hand-bearing compass.

Cruisers over about 30 feet: choose the largest card that fits your binnacle or bulkhead, with lighting and built-in compensation. Pairs of bulkhead compasses suit boats steered from either side.

Whatever you buy, install it away from speakers and wiring, swing it, and keep a deviation card at the helm.

Related planning decisions

• Marine GPS for small boats
• Chartplotters for sailboats
• Marine binoculars

Sources and photograph credits

• Plastimo Iris 100: manufacturer documentation
• Plastimo Offshore 135: manufacturer documentation
• Plastimo Offshore 75: manufacturer documentation
• Ritchie Explorer B-51: manufacturer documentation

• Liquid compass on a sailing yacht by Stefan Ivanovich, CC BY-SA 4.0. Display crops and JPEG recompression may apply; image adaptations retain the indicated license. Photo licensing does not imply endorsement.

Reviewed 20 October 2026. Specification-led editorial guidance, not a claim of hands-on testing. Recheck models, manuals, availability and prices before purchase.