A compass shows which way is north. Its magnetised needle turns to line up with Earth’s magnetic field, which is made by molten iron in Earth’s outer core. It points to magnetic north, not the North Pole, and magnetic north moves about 36 km a year. Compasses were first used in China about 1,000 years ago.
the compass quick facts
- A compass needle lines up with Earth’s magnetic field.
- Compasses point to magnetic north, not the geographic North Pole.
- Magnetic north is drifting about 36 km a year.
- Early Chinese compasses pointed south.
- Your phone uses a map of Earth’s magnetic field to find north.
What is a compass?
A compass is a tool that shows you which way is north. With north worked out, you can find south, east and west too, and use them to find your way.
A magnetic compass has a magnetised needle that can spin freely. National Geographic explains that the needle turns to line up with Earth’s magnetic field, so its two ends point towards Earth’s north and south magnetic poles.
Compasses have helped sailors, explorers, hikers and pilots find their way for about a thousand years. Today, a compass even works inside your phone.
| Compass at a glance | |
|---|---|
| What it does | shows the direction of magnetic north |
| How it works | a magnetised needle lines up with Earth’s magnetic field |
| First used | in China, about 1,000 years ago |
| First practical sea compass in Europe | about 1274, in Venice |
| Magnetic north today | in the high Arctic, drifting about 36 km a year |
| Inside phones | the World Magnetic Model |
How does a compass work?
Earth acts like a giant magnet. The British Geological Survey (BGS) says its magnetic field is made deep inside the planet, in the liquid outer core, where slowly moving molten iron carries electric currents.
NASA says Earth’s fast spin and its molten nickel-iron core work together to create this field. Scientists call the process a dynamo.
A compass needle is a small magnet. When it is free to turn, it swings round until it lines up with Earth’s magnetic field, like a tiny arrow pointing along invisible lines.
The BGS says Earth’s magnetic field acts roughly like a huge bar magnet at the centre of the planet, tilted about 10 degrees away from the line Earth spins around.
Everyday changes in Earth’s field make a compass needle wobble by no more than a few tenths of a degree, the BGS says, which is far too small to notice.
Magnets pull on each other in the same way, which is why a magnet held near a compass can make the needle swing. Discover more in our magnet facts.
Magnetic north and true north
Here is a surprise: a compass does not point to the North Pole. It points to magnetic north.
The BGS explains that magnetic north is the direction a compass needle points as it lines up with Earth’s magnetic field. True north is the direction to the geographic North Pole, the top of the imaginary line Earth spins around.
The angle between true north and magnetic north is called magnetic declination, National Geographic says. Sailors and pilots call it variation.
Declination is different in different places, and it changes over time, the US National Oceanic and Atmospheric Administration (NOAA) says. That is why navigation maps have to be updated.
There is even a third north. The BGS says grid north is the direction the blue grid lines point on Ordnance Survey maps in Britain.
In November 2022, true north, grid north and magnetic north lined up at Langton Matravers in Dorset. The BGS says it was the first time this had happened in Britain in recorded history. The meeting point then crept north and left England at Berwick-upon-Tweed on 13 December 2025.
Magnetic north is on the move
Magnetic north does not stay in one place. NOAA says the explorer James Clark Ross found the north magnetic pole in northern Canada in 1831.
The BGS says magnetic north stayed in Canada for about 400 years, moving about 10 km a year between 1600 and 1990. Then it sped up, to a record 55 km a year in the 2000s, heading towards Russia.
Now it is slowing down. NOAA’s newest report, published in January 2026, measured the north magnetic pole drifting about 36 km a year, and the south magnetic pole about 9 km a year.
In 2025, NOAA modelled the north magnetic pole in the high Arctic, less than 500 km from the geographic North Pole.
Earth’s whole magnetic field is changing too. The BGS says it is getting weaker by about 6% every century, and NASA says the field has flipped completely many times in Earth’s history, about every 300,000 years on average.
The history of the compass
Long before compasses, people discovered natural magnets. The Science Museum in London says the word “magnet” comes from Magnesia, a district in Greece rich in a magnetic rock called magnetite. A naturally magnetic piece of magnetite is called a lodestone.
The first compasses came from China. National Geographic says early Chinese compasses pointed south, and were called “south-pointing spoons”. The Science Museum says that around 1000 CE, people in China found that lodestones or magnetised iron placed in bowls of water always lined up north to south.
IEEE Spectrum, the magazine of the world’s largest engineering organisation, says a Chinese book from 1040 describes an “iron fish” floating in water that pointed south. In 1088, the scholar Shen Kuo described rubbing a needle with lodestone so that it pointed south, and hanging it from a single silk thread.
National Geographic says explorers from China and Europe were using compasses to cross the seas by the 1100s. Very early compasses were simply a magnetised needle stuck in a piece of wood or cork, floating in a dish of water.
A NOAA article by The Mariners’ Museum says the Venetians seem to have made the first practical compass in 1274, with a magnetised needle under a card showing the directions. After 1311, it says, pictures of ships almost always show a compass. Read more about the continent where this happened in our Europe facts.
Early compass needles lost their magnetism, the Science Museum says, so sailors carried a lodestone and “touched” the needle to it to re-magnetise it.
Scientists kept studying magnets. The Science Museum says Petrus Peregrinus wrote down how magnets behave in about 1269, and in 1600 William Gilbert published the first careful experiments on magnetism.
Types of compass
The classic compass is a magnetic compass, with a needle that points to magnetic north.
Ships and planes also use gyrocompasses. National Geographic says the gyrocompass, invented in the early 20th century, uses a fast-spinning wheel called a gyroscope to point to true north instead of magnetic north.
Your phone has a compass too. NOAA says the World Magnetic Model, a detailed map of Earth’s magnetic field, comes built into Android phones and iPhones, so it is used by more than a billion devices.
How people use compasses
NOAA says the World Magnetic Model is used by planes, ships, submarines and GPS units, as well as phones. It is made by NOAA and the BGS together.
The current version, WMM2025, was released on 17 December 2024 and runs until the end of 2029. A new version comes out every five years, because the magnetic field keeps changing.
NOAA says WMM2025 marks “blackout zones” near the North and South Poles, where the magnetic field can be too unreliable for navigation. Explorers in places like Antarctica have to take extra care.
Using a compass with a map
Hikers often use a compass and a map together. The compass shows north, and the map shows where paths, hills and rivers are.
Because magnetic north and map north are not quite the same, hikers adjust for declination. The BGS says declination varies by about 5 degrees across the UK, from the south-east to the north-west.
Make your own compass
NOAA’s National Ocean Service has a simple activity for making your own compass. Ask an adult to help, because needles are sharp.
You need a sewing needle 2.5 to 5 cm long, a small bar magnet or fridge magnet, a cork, a glass of water and pliers.
First, rub the magnet along the needle a few times, always in the same direction. This magnetises the needle. Next, cut a thin round slice of cork, and carefully push the needle through it with the pliers so equal lengths stick out on each side.
Half-fill the glass with water and float the cork on top. NOAA says the needle will turn to point towards the nearest magnetic pole. The floating cork lets it spin easily.
NOAA also says to keep magnets away from bank cards and some electronic devices.
Three things people get wrong
A compass does not point to the North Pole. It points to magnetic north, which is in a different place.
Magnetic north does not stay still. It moves across the Arctic by tens of kilometres a year.
Earth’s magnetic field is not fixed. It is slowly weakening and has flipped many times.
Did you know? In 2022, true north, grid north and magnetic north lined up in Britain for the first time in recorded history.
Try it
With an adult, make NOAA’s floating compass: magnetise a needle with a magnet, push it through a slice of cork and float it in water.
Knowledge check
What makes Earth’s magnetic field?
Show answer
Moving molten iron in the liquid outer core.
What is magnetic declination?
Show answer
The angle between true north and magnetic north.
Frequently asked questions
How does a compass work?
A compass has a magnetised needle that can spin freely. It turns to line up with Earth’s magnetic field and points towards magnetic north.
Does a compass point to the North Pole?
No. It points to magnetic north, which is in a different place from the geographic North Pole. The angle between them is called declination.
Who invented the compass?
The first compasses came from China. Records from 1040 and 1088 describe magnetised iron and needles pointing south.
Does magnetic north move?
Yes. It raced at up to 55 km a year in the 2000s and NOAA measured it moving about 36 km a year in its January 2026 report.
Does my phone have a compass?
Yes. Phones use magnetic sensors and the World Magnetic Model, a map of Earth’s magnetic field built into Android phones and iPhones.
How can I make a compass at home?
Rub a needle with a magnet, push it through a slice of cork and float it in water. Ask an adult to help with the sharp needle.
Sources
- NOAA National Centers for Environmental Information: wandering magnetic poles — the north magnetic pole’s discovery and movement; its pages on the World Magnetic Model and its 2024 and 2026 reports were also used
- British Geological Survey: Earth’s magnetic field — where the field comes from, its tilt and weakening; its 2024 to 2025 news on magnetic north and the three norths was also used
- National Geographic Education: compass — how a compass works, declination, early compasses and the gyrocompass
- Science Museum, London: the history of magnets — lodestones, early Chinese compasses, Peregrinus, Gilbert and re-magnetising needles
- IEEE Spectrum: history lesson, the magnetic compass — the 1040 iron fish and Shen Kuo’s 1088 needle
- NOAA National Ocean Service: make a compass — the home compass activity and safety notes; a NOAA Mariners Weather Log article on early sea compasses was also used
