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Decimal degrees vs DMS: how to read and convert GPS coordinates

· 4 min read

The same point on Earth can be written two very different ways. One looks like 40.712800; the other like 40°42'46"N. Both are correct — they are just two notations for the same latitude and longitude. Here is how to read each and switch between them.

Decimal degrees (DD)

Decimal degrees express the angle as a single number with a fractional part: 40.712800, -74.006000. The sign carries the direction — positive latitude is north, negative is south; positive longitude is east, negative is west. It is compact, easy to store, and the format almost every app, spreadsheet, and mapping API expects.

Degrees, minutes, seconds (DMS)

DMS splits each coordinate into three parts, like an hour split into minutes and seconds:

  • Degrees (°) — the whole-number part.
  • Minutes (') — each degree divided into 60 minutes.
  • Seconds (") — each minute divided into 60 seconds.

So 40°42'46"N means 40 degrees, 42 minutes, 46 seconds north. Instead of a minus sign, DMS uses a hemisphere letter — N or S for latitude, E or W for longitude. You will see DMS on paper maps, nautical charts, and aviation plates.

Converting DMS to decimal

The formula is simple — add up the parts, dividing minutes by 60 and seconds by 3600:

decimal = degrees + (minutes / 60) + (seconds / 3600)

For 40°42'46": 40 + (42 / 60) + (46 / 3600) = 40.7128. If the letter is S or W, make the result negative.

Converting decimal to DMS

Work backwards from 40.7128:

  • The degrees are the whole number: 40.
  • Multiply the remainder by 60 for minutes: 0.7128 × 60 = 42.77 → 42 minutes.
  • Multiply that remainder by 60 for seconds: 0.77 × 60 ≈ 46 → 46 seconds.

Result: 40°42'46"N (north, because the original was positive).

Which one should you use?

Use decimal degrees for anything digital — apps, links, code, and spreadsheets handle it cleanly. Reach for DMS when you are reading a paper map or working with charts that use it. The good news: you rarely have to do the math. When you find your coordinates with My Location, both formats are shown side by side and either is one tap to copy.