Compasses don’t point to true north. They point to magnetic north, which is a different location that shifts over time. As of 2025, the North Magnetic Pole sits at about 86°N latitude and 139°E longitude, roughly 1,200 miles away from the Geographic North Pole that maps are based on. That gap means your compass is always slightly “off,” and how far off depends on where you’re standing on the planet.
Magnetic North vs. True North
Earth’s core generates a magnetic field, and a compass needle aligns with that field. The point it aims toward is the North Magnetic Pole, a spot that has nothing to do with the axis the Earth spins around. The Geographic North Pole (true north) is the fixed point at the top of that axis, and it’s the reference used for maps, GPS, and navigation charts.
Because these two “norths” are in different places, a compass reading is inherently imprecise unless you account for the difference. In some locations the error is barely noticeable. In others, it can throw you off by 20 degrees or more, which over a few miles of hiking adds up to a serious wrong turn.
What Magnetic Declination Means for You
The angle between where your compass points (magnetic north) and where true north actually is has a name: magnetic declination. If magnetic north falls to the east of true north from your location, declination is positive. If it falls to the west, it’s negative. This angle changes depending on your latitude and longitude, and it also changes over time as the magnetic pole drifts.
In the eastern United States, for example, declination is typically west, meaning your compass points slightly west of true north. In Alaska, the declination can be enormous. If you’re navigating with a topographic map, you need to know the local declination and adjust your bearings accordingly. Many hiking compasses have a built-in adjustment ring for exactly this purpose. Smartphone GPS apps handle this automatically, which is one reason people rarely notice the discrepancy in everyday life.
The Magnetic Pole Is Moving
The North Magnetic Pole isn’t stationary. It has been drifting from the Canadian Arctic toward Siberia, currently moving at about 55 kilometers (34 miles) per year in a north-northwest direction. This pace accelerated significantly in the late 20th century, which forced scientists to update their models more frequently.
The standard reference for Earth’s magnetic field is the World Magnetic Model, maintained jointly by the U.S. and U.K. The current version, WMM2025, was released in December 2024 and will remain valid until late 2029. A new version comes out every five years to keep up with changes in the field. This model is what GPS systems, military navigation, and aviation instruments rely on behind the scenes.
Why Compasses Struggle Near the Poles
A compass needle doesn’t just swing horizontally. Earth’s magnetic field lines plunge into the ground at steep angles near the poles, and the needle tries to follow. This vertical pull is called magnetic dip or inclination. At the equator, field lines run roughly parallel to the surface and the needle stays level. Near the magnetic poles, the lines point almost straight down, which can cause the needle to tilt so steeply it sticks against the housing or gives erratic readings.
This is why compasses designed for use in one hemisphere often don’t work well in the other. Manufacturers add a small counterweight to one end of the needle to compensate for the local dip angle, but that fix only works within a certain range of latitudes. If you travel from North America to Australia with the same compass, you may notice the needle dragging or refusing to settle.
Nearby Objects That Throw Off Your Compass
Even away from the poles, a compass can give a wrong reading if something nearby creates its own magnetic field. This is called magnetic deviation, and it’s separate from declination. Common culprits include:
- Electronics: Cell phones, radios, speakers, and anything with a magnet or electric current can pull the needle off course.
- Metal objects: Cars, belt buckles, steel-frame buildings, and even the metal in a backpack zipper can interfere if they’re close enough.
- Natural mineral deposits: Iron-rich rock formations can distort the local magnetic field. Some volcanic areas are notorious for unreliable compass readings.
- Power lines: High-voltage electrical lines generate their own magnetic fields, which fade with distance but can easily skew a reading within a few dozen meters.
Pilots deal with this routinely. Metal in an aircraft’s body and its electronic instruments create persistent deviation, so aviation compasses come with a correction card specific to each plane. For hikers and backpackers, the practical rule is to hold the compass away from your body, step back from vehicles, and keep your phone out of the hand holding the compass.
Could the Poles Ever Flip Entirely?
Yes, and they have many times. Earth’s magnetic field has reversed polarity repeatedly throughout its history, with the last full reversal happening about 780,000 years ago. During a reversal, the field weakens dramatically (by as much as 90% at the surface) before rebuilding in the opposite orientation. A compass during that transition would behave unpredictably, potentially pointing south or wandering between directions.
These reversals are random. They’ve happened as often as every 10,000 years and as infrequently as every 50 million years. The field’s average intensity has dropped by about 10% since scientists first began measuring it in the 1830s, which occasionally sparks speculation about an impending flip. The U.S. Geological Survey’s assessment: almost certainly not happening anytime soon. The current weakening is well within the range of normal fluctuation, and the transition itself would take hundreds to thousands of years, not happen overnight.
So compasses reliably point toward magnetic north, but “north” on a compass and “north” on a map are never quite the same place. For casual use, the difference rarely matters. For serious navigation in the backcountry, at sea, or in the air, correcting for that difference is one of the most fundamental skills there is.