Latitude and Longitude Explained
Every place on Earth has an address made of two numbers. Once you can read them, you can find any point on any map, and you never have to guess which number comes first.
Why the Earth needs a grid
A sphere has no corners, no edges and no obvious starting point, so there is no natural way to say where something is. Latitude and longitude solve that by draping an imaginary grid over the planet: one set of lines running around it, another set running over the top of it. Give someone the two numbers where those lines cross and you have described a single point on Earth, to whatever precision you like.
The two numbers are always measured in degrees, because they are angles measured from the centre of the Earth rather than distances across its surface. That is the one idea that makes everything else in this lesson make sense.
Latitude: how far north or south
Lines of latitude run east to west, in circles parallel to each other, which is why they are also called parallels. They never meet and never cross. Latitude is measured from the equator, which is defined as 0 degrees, up to 90 degrees at the North Pole and 90 degrees at the South Pole.
Because the parallels are evenly spaced, one degree of latitude is very nearly the same distance everywhere on Earth: about 111 km, or roughly 69 miles. That makes latitude the easy half of the pair.
Longitude: how far east or west
Lines of longitude run from pole to pole. They are called meridians, and unlike parallels they all meet, twice, at the North and South Poles. Longitude is measured from the Prime Meridian, which runs through Greenwich in London and is defined as 0 degrees, out to 180 degrees east and 180 degrees west, where the two meet again on the far side of the planet.
Because meridians converge, one degree of longitude is not a fixed distance. At the equator it is about 111 km, the same as a degree of latitude. At 60 degrees north, near Oslo or Anchorage, it is only about 55 km. At the poles it is nothing at all. This is the detail most people miss, and it is the reason distances on a map cannot be read straight off the coordinate numbers.
Reading a coordinate pair
A written coordinate has four parts: the latitude number, its hemisphere, the longitude number, and its hemisphere. The hemisphere letters matter as much as the numbers. Dropping the S from a southern latitude moves the point to the opposite side of the equator.
Two ways of writing the same place
You will meet coordinates in two notations. The older one splits each degree into 60 minutes, and each minute into 60 seconds, exactly like an hour: 48 degrees, 51 minutes, 24 seconds north. The modern one, used by phones, GPS units and almost every mapping website, writes the whole thing as a single decimal number: 48.8566 north.
They describe the same point. Converting between them is arithmetic you can do on paper, and it is worth doing once by hand so the notation stops looking like a code.
Worked example
Convert 51 degrees, 28 minutes, 38 seconds north to decimal degrees.
- 28 minutes ÷ 60 = 0.4667 degrees
- 38 seconds ÷ 3600 = 0.0106 degrees
- 51 + 0.4667 + 0.0106 = 51.4773
The answer is 51.4773 degrees north, which is the Royal Observatory at Greenwich.
Reference lines worth memorising
Six lines account for most of the coordinates you will ever need to place at a glance.
| Line | Coordinate | What it marks |
|---|---|---|
| Equator | 0 degrees latitude | Divides the northern and southern hemispheres |
| Tropic of Cancer | 23.5 degrees N | The furthest north the sun is ever directly overhead |
| Tropic of Capricorn | 23.5 degrees S | The furthest south the sun is ever directly overhead |
| Arctic Circle | 66.5 degrees N | Above it, at least one day of midnight sun each year |
| Prime Meridian | 0 degrees longitude | Runs through Greenwich; longitude is measured from it |
| 180th meridian | 180 degrees E or W | Roughly follows the International Date Line |
The tropics sit at 23.5 degrees because that is the tilt of the Earth on its axis. The Arctic and Antarctic Circles are the same tilt subtracted from 90.
Check what you learned
Five questions on coordinates. Pass at 70% or better to complete the lesson and earn points.
Practice with Games
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Latitude and longitude, in one paragraph
Latitude tells you how far north or south of the equator a place is, measured in degrees from 0 at the equator to 90 at each pole. Longitude tells you how far east or west of the Prime Meridian it is, from 0 at Greenwich to 180 degrees in either direction. Latitude is always written first. Because lines of latitude are parallel, a degree of latitude is about 111 km anywhere on Earth; because lines of longitude converge at the poles, a degree of longitude shrinks from about 111 km at the equator to nothing at the poles. Coordinates appear either as degrees, minutes and seconds, or as decimal degrees, and you convert between them by dividing the minutes by 60 and the seconds by 3600.
Common questions about latitude and longitude
Which comes first, latitude or longitude?
Latitude always comes first, followed by longitude. The pair 48.8566 N, 2.3522 E is Paris. Reversed, it becomes a point in the Indian Ocean. Almost every mapping tool expects latitude first, and none of them will warn you if you swap the two.
What is the difference between latitude and longitude?
Latitude measures distance north or south of the equator and runs in parallel circles that never meet. Longitude measures distance east or west of the Prime Meridian and runs in lines from pole to pole that meet at both ends. Latitude tops out at 90 degrees, longitude at 180.
How do I convert degrees, minutes and seconds to decimal degrees?
Divide the minutes by 60, divide the seconds by 3600, then add both to the whole degrees. For 51 degrees 28 minutes 38 seconds: 28 divided by 60 is 0.4667, 38 divided by 3600 is 0.0106, and 51 plus 0.4667 plus 0.0106 gives 51.4773 degrees.
How far apart is one degree of latitude or longitude?
One degree of latitude is about 111 km or 69 miles, and that stays almost constant everywhere. One degree of longitude is about 111 km at the equator but shrinks as you move towards the poles, because the meridians converge. At 60 degrees north it is roughly half that, and at the poles it is zero.
Why is the Prime Meridian in Greenwich?
There is no natural zero for longitude, unlike latitude which has the equator. Countries used their own starting meridians for centuries. Greenwich was adopted as the international standard at a conference in 1884, largely because most of the world shipping already used charts based on it.