A compass is the one navigation tool that never runs out of battery, never loses signal and works in cloud, fog and darkness. Phones are brilliant until the screen dies in the cold, the battery drains or you drop signal on a hill, and that's exactly when a map and compass earn their place. For UK walking, a good baseplate compass is inexpensive, lasts decades and is the backbone of safe navigation off marked paths.
This guide covers the main types, the features that genuinely matter for Ordnance Survey maps, and what a beginner actually needs versus what's nice to have. It pairs with learning the skills — a compass only helps if you know how to take and follow a bearing — but buying the right one makes learning easier.
Baseplate vs mirror (sighting) compasses
A baseplate compass is the standard UK hill-walking compass: a rotating bezel on a clear plastic plate you lay directly on the map. It's light, simple and does everything most walkers need — taking bearings off the map, following them on the ground, and measuring distance with the scales on the edge. For the vast majority of UK walkers, this is the right buy.
A mirror or sighting compass adds a hinged lid with a mirror and sighting notch, letting you aim at a distant feature and read the bearing at the same time for more precise sightings. It's the choice for serious mountain navigation, longer expeditions or anyone who wants the extra accuracy, and the mirror doubles as an emergency signalling aid. It costs more and is bulkier, so it's overkill for gentle low-level walks.
Features that matter for OS maps
Look for romer scales printed on the baseplate that match UK Ordnance Survey maps — usually 1:25,000 (Explorer) and 1:50,000 (Landranger). These let you measure grid references and distances directly. A clear baseplate and a magnifying lens help you read fine detail and contour lines, and a lanyard keeps the compass to hand and out of the mud.
A liquid-filled capsule steadies the needle so it settles quickly rather than swinging — essential on a windy hill. Luminous or glow markings on the bezel and needle help in poor light and at dawn or dusk. Look for a bezel with clear degree markings, and ideally a small stopper or grip so you can turn it accurately with cold or gloved hands.
Declination and the moving-magnetic-north question
Magnetic north drifts over time and differs from grid north on your map. In much of the UK this difference is now small — close to zero in many areas — but it varies by location and year, so it's worth knowing. A compass with an adjustable declination scale lets you set the correction once and forget it, which is handy if you also walk abroad where the difference is larger. For UK-only use it's a convenience rather than a necessity.
If you buy a fixed compass, you simply apply the small correction manually when converting between grid and magnetic bearings. Any good UK walking guide or navigation course explains this in a few minutes — it's not a reason to overspend.
Global needles and buying for abroad
The Earth's magnetic field tilts the needle differently depending on where you are (magnetic dip). Compasses are balanced for a zone; a standard UK/northern-hemisphere compass works fine across Britain and Europe. If you'll navigate in the southern hemisphere or the tropics, buy a global-needle compass balanced for worldwide use so the needle stays level. For UK-only walking, a standard needle is all you need.
What a beginner actually needs
Start with a good-quality liquid-filled baseplate compass with UK romer scales, clear markings and a lanyard. It'll cover map work, bearings and navigation in poor visibility, and it'll still be working in twenty years. Add a mirror compass, adjustable declination or a global needle only if your walking genuinely calls for them. More important than any feature is practising with map and compass together before you rely on them in bad weather.
How to choose in one line
For UK hill walking, buy a liquid-filled baseplate compass with 1:25,000 and 1:50,000 romer scales, a magnifier and a lanyard. Step up to a mirror sighting compass for mountain and expedition use, add adjustable declination if you also walk abroad, and choose a global needle only if you'll navigate far from the northern hemisphere.
