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How to read GPS coordinates — a plain-English guide

· 5 min read

GPS coordinates are just two numbers — latitude and longitude — that together pin any spot on Earth to within a few meters. But when you first encounter them, formats like 40° 26' 46.56" N, 79° 58' 21.99" W or 40.44626, -79.97277 can feel cryptic. This guide decodes them in plain English: what each number means, how the different formats relate to each other, and how to actually use coordinates once you have them.

What the two numbers represent

Latitude is how far north or south you are from the equator. The equator is 0°. The North Pole is +90° (or 90° N). The South Pole is -90° (or 90° S). Every point on Earth has a latitude between those extremes. A latitude of 40° puts you roughly at the level of New York, Madrid, or Beijing.

Longitude is how far east or west you are from the prime meridian — an imaginary line running through Greenwich, England. The prime meridian is 0°. Going east you reach +180°; going west you reach -180°. Both +180° and -180° are the same physical line, known as the International Date Line, in the Pacific Ocean.

Together, one latitude and one longitude uniquely identify a single point on Earth. Always write latitude first, longitude second — it's the universal convention. Swapping them puts you on the wrong side of the planet.

The three formats you'll encounter

GPS coordinates come in three common formats, all describing the same point. Let's use Pittsburgh, Pennsylvania as an example:

Decimal Degrees (DD)

40.44626, -79.97277

This is the format most software and APIs prefer. Each coordinate is a single decimal number. Positive latitude = north, negative = south. Positive longitude = east, negative = west. The minus sign before longitude is how you know it's west of Greenwich. This is what most map apps, navigation software, and GPS converters use by default.

Degrees Minutes Seconds (DMS)

40° 26' 46.56" N, 79° 58' 21.99" W

The traditional format, still used on many paper maps, military documents, and older navigation equipment. Each coordinate is broken into degrees (°), minutes ('), and seconds ("). There are 60 minutes in a degree and 60 seconds in a minute — just like time. The N/S and E/W letters replace the +/- convention. To convert between DMS and decimal degrees, the maths is: decimal = degrees + minutes/60 + seconds/3600.

Degrees Decimal Minutes (DDM)

40° 26.776' N, 79° 58.366' W

A hybrid format common in marine navigation and some handheld GPS units. The degrees are whole numbers; the minutes include a decimal fraction; seconds are dropped. Less common than the other two but you'll encounter it on nautical charts and some aviation tools. The coordinate converter handles all three formats.

Reading precision from decimal places

In decimal degrees, the number of decimal places tells you how precise the coordinate is:

  • 1 decimal place — about 11 km precision (city level)
  • 2 decimal places — about 1.1 km (town level)
  • 3 decimal places — about 111 meters (street level)
  • 4 decimal places — about 11 meters (building level)
  • 5 decimal places — about 1.1 meters (useful for most navigation)
  • 6 decimal places — about 11 centimeters (surveying grade)

Most smartphone GPS hardware is accurate to 3–5 meters in good conditions, so 5 decimal places is more than sufficient to record or share a position. For a full breakdown of GPS accuracy, including the difference between horizontal and vertical accuracy, see the dedicated article.

Common mistakes when using GPS coordinates

  • Swapping lat and lng — the most common error. Latitude always comes first. 40.4, -79.9 is Pittsburgh; -79.9, 40.4 is in the ocean near Antarctica.
  • Missing the negative sign — 79.97277 (no minus) is in China. -79.97277 is Pennsylvania. The sign matters.
  • Copying truncated coordinates — copying only 2 decimal places from a 5-decimal source can shift your position by over a kilometer.
  • Mixing formats — entering DMS values into a field that expects decimal degrees, or vice versa. Always confirm which format a form or app expects.

How to find and use GPS coordinates

To find your current GPS coordinates, open My Location in any browser and tap Show my location. Your latitude, longitude, and address appear immediately. You can copy the coordinates in any of the three formats and paste them directly into Google Maps, Apple Maps, WhatsApp, or any navigation app. If someone sends you coordinates and you need to convert them to a different format, the coordinate converter handles it in seconds.