How to Use a Compass: Take a Bearing, Adjust for Declination, Walk a Straight Line

Most people carry a compass for years without ever learning how to use a compass properly. They know the red needle points north. That is about where it stops.

The needle is the least interesting part. The useful skill is taking a bearing, correcting it for your local declination, and then walking that line across ground where you cannot see your destination. That is a hand skill. It takes an afternoon in a park to learn and about 10 minutes a year to keep.

Here is the whole thing, in order, with the numbers that matter.

How do you use a compass, step by step?

Five steps, in this order: orient the map, take the bearing, adjust for declination, follow the bearing, and confirm your position.

1. Orient the map. Lay the compass flat on the map with the orienting lines parallel to the map's north lines. Turn the map and the compass together until the red needle sits inside the orienting arrow. The map now matches the ground in front of you.

2. Take the bearing. Either sight a landmark on the ground, or lay the baseplate edge between two points on the map. Turn the dial until the needle is boxed, then read the number at the index line.

3. Adjust for declination. Add or subtract your local value so the map number and the compass number agree.

4. Follow the bearing. Hold the compass level, turn your body until the needle is boxed again, and walk toward whatever the direction of travel arrow points at.

5. Confirm your position. Shoot bearings to 2 or 3 features you can identify on the map and see on the ground, then draw them back.

Everything below is detail on those 5 moves.

What are the parts of a baseplate compass, and why not a button compass?

A baseplate compass has 8 working parts, and a button compass has 1. That difference is the whole argument.

The Princeton Outdoor Action guide to map and compass lists them: the base plate, the straight edge and ruler, the direction of travel arrow, the compass housing marked in 360 degrees, the north label, the index line, the orienting arrow, and the magnetic needle with its red north end.

Here is what each one buys you:

• The straight edge lets you lay a line between two points on a map. A button compass cannot do this at all.

• The rotating housing stores a number. You set a bearing once and it stays set while you walk, climb over deadfall, and stop for water.

• The orienting arrow is what you "box" the needle inside. It is how you re-find the same line 40 times in a mile.

• The index line is the single place you read the bearing from, so two people reading the same compass get the same number.

A button compass sewn onto a pack strap tells you which way is roughly north. That is genuinely useful for a rough heading, and it is better than nothing. It cannot take a bearing off a map, hold that bearing, or let you triangulate. Carry one as a backup. Do not make it the plan.

How do you use a compass to take a bearing off the land?

Point, turn the dial until the needle is boxed, and read the number. That is it.

Princeton's guide breaks it into 3 moves. Point the direction of travel arrow at the thing you want a bearing to, whether that is a peak, a tower, or a notch in a ridge. Rotate the compass housing until the orienting arrow lines up under the red magnetic needle, which is the move everyone calls "boxing the needle." Read the bearing at the index line.

Two habits make this reliable instead of approximate:

• Hold the compass level and roughly at chest height, with the direction of travel arrow pointing straight away from your sternum. If the baseplate is tilted, the needle drags and the reading wanders.

• Turn your whole body, not just your wrists. It sounds trivial. It is the difference between a 2 degree error and a 10 degree one.

Take the bearing twice, a few seconds apart, and see if you get the same number. If you do not, something nearby is pulling the needle. More on that below.

How do you take a bearing off a map?

Lay the baseplate edge along the line you want to travel, then turn the dial until the orienting lines match the map's north lines.

Princeton's map procedure is short: put the edge of the baseplate so it connects where you are to where you are going, rotate the compass housing until the orienting lines run parallel to the map's north lines, then read the bearing at the index line. Notice what you did not do. You never looked at the needle. On a map you are measuring an angle on paper, so the magnetic needle is irrelevant for that moment.

That is exactly why the next step exists. The number you just read is a true bearing, measured against the map's north. Your compass in the field reads magnetic. Those are two different norths, and the gap between them is declination.

If the map itself is new to you, it is worth spending a session on how to read a topographic map first. Contour lines and scale are what turn a bearing into a plan.

What is magnetic declination, and how do you adjust for it?

Magnetic declination is the angle between magnetic north and true north, and you correct for it by adding it with its sign.

NOAA's National Centers for Environmental Information defines it plainly on its magnetic declination page: declination is "the angle between magnetic north and true north," it "is positive east of true north and negative when west," and you "compute the true bearing from a magnetic bearing by adding the magnetic declination to the magnetic bearing."

So the one rule to memorize is:

• True bearing = magnetic bearing + declination, where east is a plus number and west is a minus number.

• Going the other way, from a map bearing to something you can walk, you flip it: magnetic bearing = true bearing minus declination.

Worked example. You measure 85 degrees off the map and your local declination is 12 degrees east. The National Wildfire Coordinating Group declination lesson works this exact case: 85 minus 12 gives you 73 degrees to set on the compass. Its rule of thumb is "magnetic = true minus easterly declination" and "magnetic = true plus westerly declination," which old hands shorten to "west is best, east is least."

If your compass has an adjustable declination screw, set it once at the trailhead and stop doing arithmetic in the rain. Princeton notes this option: you rotate the inner ring so the needle parks on the declination angle instead of on 360, and after that every number you read is already corrected.

How do you find your local declination value?

Use the NOAA NCEI declination calculator with today's date and your latitude and longitude. Do not trust the diagram printed on the map.

The USGS explains its three north arrows this way: the star is true north, GN is grid north, and MN is magnetic north, which shows "the direction a magnetic compass would point at the time the map was published." USGS is blunt elsewhere that the map collar shows the declination for the year the map was made, and points readers at NOAA's calculator for a current number.

Why the map value goes stale:

• NOAA updates the World Magnetic Model every 5 years. WMM2025 came out on December 17, 2024 and runs until late 2029.

• The north magnetic pole itself is moving. NOAA's geomagnetism FAQ puts it at roughly 55 km per year, north-northwest.

• Princeton's guide describes the field drifting west at about 1 degree every 5 years. The Wisconsin State Cartographer's Office measures the local version of that: about 6.5 minutes of westerly shift per year, which it notes is about 11 miles of ground movement for the line.

The spread is large enough that guessing is not an option. NWCG puts the North American range at 30 degrees east in Alaska to 20 degrees west in Labrador. Inside the lower 48, Princeton gives roughly 20 degrees west in Maine to roughly 21 degrees east in Washington. The zero line, where magnetic and true north agree, currently runs through Wisconsin, where the State Cartographer's Office lists Door County at about 4 degrees west and west-central Wisconsin at about 1.5 degrees east.

The calculator is good. NOAA's help page for the declination calculator says accuracy is "generally within 30 minutes (0.5 degrees) of arc." Write the number on the map in pencil with the date next to it. Check it again next season.

How do you follow a bearing without drifting off line?

Stop trying to walk while staring at the compass. Pick a landmark that sits on your bearing, walk to it, then pick the next one.

Nobody walks a straight line by needle alone. You step around a blowdown, you contour around a wet spot, and by the third detour you are 30 degrees off without noticing. The fix is to let the terrain hold the line for you:

• Intermediate landmarks. Box the needle, look up, and find something distinctive on that bearing: a leaning snag, a pale boulder, a gap in the canopy. Walk to it without looking at the compass. Re-shoot from there.

• Back bearings. Turn around and shoot a bearing back at where you started. Princeton gives the arithmetic: if your travel bearing is under 180 degrees, add 180 to get the back bearing. If it is over 180, subtract 180. If the back bearing does not match, you have drifted, and you can correct before it compounds.

• A pace count. This is how you turn a bearing into a distance.

For the pace count, Mississippi State University Extension's "Basic Compass Orienteering" gives the method and the starting figure: count how many paces it takes you to walk 100 meters, and remember that a pace is 2 steps, roughly 30 inches for a typical adult. Do the arithmetic and 100 meters lands near 65 paces.

That average is a starting guess, not your number. Go measure a 100 meter stretch on flat ground and count. Then count it again uphill, and again with a loaded pack. Most people find those three numbers are not close to each other.

How do you use a compass to fix your position by triangulation?

Shoot bearings to 2 or 3 features you can see on the ground and find on the map, draw each line backward, and your position is where they cross.

Princeton's sequence, when you are not sure where you are:

1. Orient the map and pick out 2 or more landmarks you can see and also identify on paper. Choose ones that sit roughly 90 degrees apart, because two landmarks close together give you a long skinny crossing instead of a point.

2. Take a bearing to the first landmark and correct it for declination.

3. Lay the baseplate on the map with its edge touching that landmark, then rotate the whole compass until the orienting arrow points to map north.

4. Draw a pencil line along the baseplate edge. You are somewhere on that line.

5. Repeat for the second landmark. Where the two lines cross is your position. A third bearing turns the crossing into a small triangle, and the size of that triangle tells you how much to trust it.

A big triangle is information, not failure. It means one of your landmarks was misidentified or one of your bearings was sloppy, and you should re-shoot before you commit to a route.

What are aiming off, handrails, and catching features?

They are three ways to be deliberately imprecise so that small errors stop mattering.

Aiming off. If you are walking to a bridge on a creek, do not aim at the bridge. Princeton's advice is to aim 3 to 5 degrees to one side on purpose. When you hit the creek, you know for certain which way to turn. Aim straight at the bridge and a 2 degree error leaves you at the water's edge with a 50-50 guess.

Handrails. A handrail is a long linear feature running roughly parallel to your route: a stream, a ridge, a fence line, a power line cut, an old road. Princeton calls these baselines. You follow them instead of following a bearing, and you save the compass work for where the handrail ends.

Catching features. A catching feature is something wide that sits across your path beyond your target and tells you that you have gone too far. A river, a highway, a lake shore, a sharp drop in the contours. Pick one before you start walking. Then overshooting becomes a piece of information instead of a problem.

These three are also your insurance when the compass is not available at all, which is its own skill set. It is worth knowing how to navigate without a compass before you need to.

What throws a compass off, and how far away do you have to hold it?

Iron and steel, live electrical current, and certain rock. There is no single published safe distance, which is exactly why you check instead of assume.

The extension guides are specific about the culprits without pretending there is one magic number. Mississippi State Extension warns that "any large pieces of metal in the area can affect the compass needle," and names two everyday cases: a pocket knife in your hand, or standing right next to an automobile. The University of Wisconsin Extension orienteering lesson plan adds that "something like a nail or even some electric wires overhead could affect the compass from reading correctly."

The practical list, in rough order of how often it bites people:

• Standing inside or right beside a vehicle. Step well clear before you shoot anything.

• A phone, a headlamp, or an earbud case in a chest pocket, inches from the compass.

• A steel belt buckle, a sheath knife on your hip, or a fixed blade in your hand.

• Power lines, metal fences, culverts, and railroad track.

• Iron-rich bedrock. NOAA's FAQ notes that local anomalies "exceeding 10 degrees of declination, although rare, do exist," and that 3 to 4 degree anomalies occur in limited areas. It describes one mapped Minnesota area at 16 degrees east with a 12 degrees west anomaly only a few miles away.

Since there is no official distance, use a test instead. Hold the compass flat at arm's length, take a bearing, then walk 20 or 30 feet away and take the same bearing again. If the two numbers disagree, something in the first spot was pulling the needle. Move and repeat until two readings from different spots agree.

When the compass and the terrain flatly disagree with each other, believe the terrain. Contour lines and drainages do not drift.

The part most guides skip: declination errors compound

A bearing error does not stay the same size. It widens the whole way, and it widens fast.

The arithmetic is just a right triangle. Over 1 mile, which is 5,280 feet:

Read the 10 degree row again. That is a plausible declination error in plenty of the country, and after one mile it puts you 930 feet to the side of where you meant to be. A trail junction is maybe 20 feet wide. A saddle you were aiming for might be 200 yards across. At 930 feet off, you walk past both and never see them, in country where you cannot see 100 feet through the trees.

Three ways this error sneaks in:

• Using the map's printed declination. A map from 1998 with the field drifting about 1 degree every 5 years is roughly 5 degrees stale. That is 460 feet per mile before you make any other mistake.

• Adding when you should subtract. Getting the sign backward does not cost you 12 degrees. It costs you 24, because you moved the wrong way by the full amount. At 12 degrees east handled backward, that is about 2,250 feet per mile.

• Correcting twice. This is the quiet one. If your compass has an adjustable declination ring already set, and then you also do the arithmetic in your head, you have double-corrected. Pick one method and stick to it.

The fix is boring and it works. Write the current declination on the map in pencil with the date. Decide once whether you correct on the dial or in your head. Re-shoot a back bearing every few hundred yards. None of that is dramatic. It is the difference between arriving and searching.

Frequently asked questions

Do I still need to know how to use a compass if I have GPS?

Yes, because a compass and a paper map have no battery, no signal requirement, and no screen to break. A phone in the cold can go from 60 percent to dead in an hour. Use the GPS as the fast tool and carry the compass as the one that always works. Knowing both means you can cross-check one against the other when a reading looks wrong.

Which direction do I add declination, east or west?

NOAA treats east as positive and west as negative, so true bearing = magnetic bearing + declination. Coming off a map and going to your compass, reverse it: subtract an easterly value and add a westerly one. NWCG shortens this to "west is best, east is least." Write your local value and its direction on the map so you never have to reconstruct the rule under stress.

How often does magnetic declination actually change?

Continuously, and enough to matter over a decade. NOAA rebuilds the World Magnetic Model every 5 years, and the north magnetic pole is moving at roughly 55 km per year. Princeton's guide describes a westward drift of about 1 degree every 5 years. A map more than 10 years old should have its declination value re-checked against the NOAA calculator before you rely on it.

What is a good pace count for 100 meters?

Around 65 paces for an average adult on flat ground, using Mississippi State Extension's figure of one pace being 2 steps at roughly 30 inches. Treat that as a starting estimate only. Measure your own over a known 100 meters, then measure it again uphill and with a full pack, because those numbers will be different and the terrain rarely cooperates.

Can my phone or knife really throw the compass off?

Yes, if they are close to it. Extension guides warn that a pocket knife in your hand or standing beside a vehicle can change the reading, and that overhead electric wires can too. The check takes 10 seconds: shoot a bearing, walk 20 or 30 feet, shoot it again. If the numbers disagree, something where you were standing was pulling the needle.

A compass is a cheap, boring tool that does exactly one job and does it in any weather, at night, with no signal and no charge. Learning how to use a compass well takes one afternoon in a park with a map, a pencil, and a measured 100 meters. Do that once and the skill stays with you. If you want a third layer under the map and the needle, learning to find north by the stars costs nothing and weighs nothing.

Start with what you have. Build from there.

You never know, but you can always be ready.

Sources: NOAA NCEI, Magnetic Declination, NOAA NCEI, World Magnetic Model, NOAA NCEI, Geomagnetism Frequently Asked Questions, NOAA NCEI, Magnetic Declination Calculator Help, USGS, What is declination?, USGS, What do the different north arrows on a USGS topographic map mean?, National Wildfire Coordinating Group, Declination, Princeton Outdoor Action, Guide to Map and Compass Part 2, Princeton Outdoor Action, Guide to Map and Compass Part 3, Mississippi State University Extension, Basic Compass Orienteering, University of Wisconsin Extension, Orienteering I Lesson Plan, Wisconsin State Cartographer's Office, Magnetic Declination.