DMS to decimal degrees converter

About this conversion

DMS (e.g. 48°51'30"N) is how coordinates traditionally appear on maps and in surveying. Decimal degrees (48.8584) is the single-number form GPS units, GeoJSON and most software expect.

Formula: DD = degrees + minutes ÷ 60 + seconds ÷ 3600, made negative for South or West.

How to use it

1. Enter your latitude and longitude above (any of decimal degrees, DMS or DDM, auto-detected).
2. Read the highlighted result and click Copy. Every other format is shown too.
3. Nothing is uploaded, it all runs in your browser.

How DMS to decimal degrees works

Decimal degrees is the same angle written as one number instead of three. The formula is simple arithmetic: decimal = degrees + minutes/60 + seconds/3600. There are 60 minutes in a degree and 60 seconds in a minute, so a minute is 1/60 of a degree (0.016667) and a second is 1/3600 (0.000278). Add the three parts and you have the decimal value.

The hemisphere sets the sign, not the arithmetic. North latitudes and east longitudes are positive; south and west are negative. So 40°26'46"S becomes -40.44611, exactly the northern value with a minus sign. Getting the sign wrong is the single most common error, and it flips a point to the opposite side of the equator or the Greenwich meridian.

Worked examples

A northern, eastern coordinate

Take the Eiffel Tower at 48°51'30"N, 2°17'40"E. Latitude: 48 + 51/60 + 30/3600 = 48 + 0.85 + 0.00833 = 48.85833. It is north, so it stays positive. Longitude: 2 + 17/60 + 40/3600 = 2.29444, positive because it is east. Result: 48.85833, 2.29444.

A southern, western coordinate

Now Rio de Janeiro's Christ the Redeemer at 22°57'6"S, 43°12'39"W. Latitude: 22 + 57/60 + 6/3600 = 22.95167, then negated to -22.95167 because it is south. Longitude: 43 + 12/60 + 39/3600 = 43.21083, negated to -43.21083 because it is west. The hemisphere letters decide the sign; the arithmetic is identical.

Seconds that round up

For 40°26'46"N, the seconds term is 46/3600 = 0.01278, giving 40.44611. Carry at least five decimal places: five decimals is roughly one metre on the ground, which is finer than a whole second of arc.

Precision and rounding

Keep enough decimal places. Each decimal place of latitude is worth roughly a factor of ten on the ground: 2 places is about 1.1 km, 3 places about 110 m, 4 about 11 m, 5 about 1.1 m and 6 about 11 cm. Since one second of arc is already about 31 m, converting DMS to only two or three decimals throws away precision the original had. Five or six decimals is the safe default for survey and mapping work.

A closer look at the numbers

It helps to know what each part of a DMS value is worth in decimal degrees. One minute is 1/60 of a degree, or 0.016667°; one second is 1/3600, or 0.000278°. So the minutes and seconds only ever add a fraction to the whole degree, they can never change it. A few common values: 15' = 0.25°, 30' = 0.5°, 45' = 0.75°, and 30" = 0.008333°. If your converted number is more than one degree away from the whole-degree part you started with, something has gone wrong, usually a minutes value mistakenly typed as degrees.

Reading the result back

To check a result, convert it back. Take the decimal part, multiply by 60 for the minutes, take that decimal part and multiply by 60 again for the seconds. For 48.85833 the fraction 0.85833 × 60 = 51.5, and 0.5 × 60 = 30, giving 48°51'30", the value you started with. If you want to go that direction for real, the decimal degrees to DMS converter does it automatically.

Quick reference

A few well-known places, converted, so you can sanity-check your own numbers against them.

Accepted input formats

The box accepts DMS in the ways people actually write it: 48°51'30"N, 48 51 30 N, 48:51:30N, or with a leading hemisphere like N48 51 30. Spaces, symbols and colons are all understood, so you can paste straight from a map margin or a survey report without reformatting.

You do not have to reformat anything first. The box detects the notation from what you paste, so every one of these is understood:

The hemisphere is taken from an N, S, E or W letter anywhere in the value, or from a leading minus sign. If both are missing, a positive number is assumed north or east.

Where you will use it

You will meet DMS on paper maps, in property deeds, on older GPS units and in aviation and marine references, because it reads naturally to a person. But almost every digital tool wants decimal degrees: spreadsheets and CSV imports, GIS software, web-mapping libraries and GeoJSON all expect a plain decimal. Converting DMS to decimal degrees is usually the first step in getting field-collected coordinates onto a map.

What to do next

Once your coordinates are in decimal degrees you can put them on a map. Drop them into a spreadsheet and use the spreadsheet to map converter, or go straight to CSV to KML for Google Earth. Going the other way, from decimal degrees back to degrees minutes seconds for a deed or a printed chart, is the decimal degrees to DMS converter.

Common mistakes to avoid

• Forgetting the hemisphere. Without the N/S/E/W letter or a sign, a southern latitude looks northern. Keep the letter with the value.
• Swapping minutes and seconds. 48°30'15" is not 48°15'30". Minutes come first, then seconds.
• Truncating too early. Rounding to two decimals loses about a kilometre; keep five or six for survey-grade work.

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