A compass tells you direction by using a magnetized needle that always aligns itself with Earth’s magnetic field. The red end of the needle points north, and every other direction is measured as a number of degrees clockwise from that north point: east is 90°, south is 180°, west is 270°, and north completes the circle at 360° (which is the same as 0°). Once you understand that single principle, reading any compass becomes straightforward.
The Four Cardinal and In-Between Directions
The four cardinal directions sit at even 90° intervals around the compass dial: North at 0°, East at 90°, South at 180°, and West at 270°. Halfway between each pair are the intercardinal directions: Northeast at 45°, Southeast at 135°, Southwest at 225°, and Northwest at 315°.
Most compasses further divide those gaps with secondary points. Between North (0°) and Northeast (45°), for example, you’ll find North-Northeast at 22.5°. Between Northeast and East sits East-Northeast at 67.5°. This pattern repeats all the way around the dial, giving you 16 named points spaced 22.5° apart. You don’t need to memorize them all. Just remember that degrees always count clockwise from north, and any direction on Earth can be described as a number between 0 and 360.
Parts of a Baseplate Compass
The most common compass for hiking and general navigation is the baseplate style, sometimes called an orienteering compass. It has a few key parts worth knowing before you start.
- Magnetic needle: A small magnetized pointer floating inside the compass housing. The red end always swings toward magnetic north; the white (or black) end points south.
- Compass housing (dial): The rotating ring marked with degrees from 0 to 360 around its edge. You turn this ring to set bearings.
- Orienting arrow: A fixed arrow printed on the floor of the housing, beneath the needle. It rotates when you turn the dial and is used to align the needle when following a bearing.
- Direction-of-travel arrow: A long arrow on the baseplate itself, pointing away from you. This is the arrow you actually follow once you’ve set your bearing.
A lensatic compass, the type used by the military, works differently. It has a sighting wire and a magnifying lens for reading the dial precisely, but it doesn’t double as a protractor the way a baseplate compass does. For most people learning compass navigation, a baseplate compass is easier to read and more versatile.
How to Find Your Heading
Hold the compass flat in front of you, about chest height, with the direction-of-travel arrow pointing straight ahead. Let the magnetic needle settle. Now look at where the red end of the needle lands on the degree markings around the dial. If the red needle points to the “N” and your direction-of-travel arrow also lines up with it, you’re facing north, or 0°.
If you want to know the exact direction you’re currently facing, turn the compass housing until the orienting arrow on the floor of the dial lines up directly beneath the red end of the magnetic needle. Then read the degree number where the housing meets the direction-of-travel arrow. That number is your heading, also called a bearing or azimuth.
A common beginner mistake is following the red needle itself. If you do that, you’ll always walk north regardless of where you actually want to go. The red needle is just your reference point. The direction-of-travel arrow is what you follow.
How to Follow a Specific Bearing
Say you need to travel at a bearing of 240°, perhaps toward a trailhead or a landmark. Start by rotating the compass housing until 240° lines up with the direction-of-travel arrow. Don’t touch the housing again after this step.
Now hold the compass level in front of you and turn your entire body (not the dial) until the red end of the magnetic needle settles inside the orienting arrow. Some people call this “boxing the needle” because the needle sits neatly inside the arrow’s outline. Once the needle is boxed, the direction-of-travel arrow points at 240°. Pick a visible landmark in that direction, walk to it, and repeat the process.
Taking a Bearing From a Map
If you’re working with a topographic map and want to find the bearing between your current position and a destination, lay the map on a flat surface and place the long edge of the compass baseplate along a line connecting the two points. Make sure the direction-of-travel arrow points toward your destination, not back toward your starting point.
Without rotating the compass itself, turn the housing until the orienting lines inside the dial are parallel to the north-south grid lines on the map, with the “N” on the housing pointing toward the top of the map. Read the degree number where the housing meets the direction-of-travel arrow. That’s your bearing. You can now pick up the compass, box the needle, and walk that heading in the field.
Why Your Compass Doesn’t Point to True North
A compass needle points to magnetic north, which is not the same as true north (the geographic North Pole). As of 2025, the magnetic north pole sits at roughly 86°N latitude, 139°E longitude, in the Arctic Ocean north of Canada, and it drifts about 55 kilometers per year in a north-northwest direction. The angle between true north and magnetic north at your location is called declination.
Declination varies depending on where you are. In parts of the eastern United States, magnetic north falls west of true north (negative declination). In much of the western U.S., magnetic north falls east of true north (positive declination). The difference can range from just a couple of degrees to 20° or more, which over a long hike could put you hundreds of meters off course.
To correct for this, check the declination value printed on your topographic map or look it up using NOAA’s World Magnetic Model (the current version, WMM2025, is valid through 2029). The rule from the U.S. Geological Survey is simple: if your local declination is positive (magnetic north is east of true north), subtract the declination from your map bearing. If the declination is negative (magnetic north is west of true north), add the declination. Some compasses have an adjustable dial that lets you set your declination once so you don’t have to do the math every time.
Orienting a Map With Your Compass
Before you start navigating, it helps to orient your map so that “north” on the paper actually faces north in the real world. Set your compass to your corrected declination bearing, then place the baseplate along the east or west edge of the map with the direction-of-travel arrow pointing toward the top. Holding the compass in place, rotate the entire map until the red needle boxes inside the orienting arrow. Now every feature on the map lines up with the terrain around you, making it much easier to identify landmarks and plan your route.
You’ll need to re-orient the map each time you pull it out, since your position and surroundings will have changed.
Avoiding Bad Readings
Magnetic interference is the biggest source of compass errors. Metal objects and electronics generate their own magnetic fields that pull the needle away from north. Keep the compass away from your car, belt buckles, watches, phones, and battery packs. Steel bridges, pipelines, and even natural iron ore deposits in the ground can throw off readings by tens of degrees. In cities, steel buildings create zones where the needle becomes unreliable.
The other frequent mistakes are simpler. Holding the compass at an angle instead of level lets the needle drag against the housing and give a false reading. Not pointing the direction-of-travel arrow straight ahead of you skews the result. And forgetting to account for declination adds a consistent error to every bearing you take. Build the habit of checking these three things (level, aligned, declination-corrected) each time you use the compass, and your readings will be accurate enough for confident navigation on any trail.