What the Coordinate Format Converter does
This converter reads a latitude and longitude written in any common format - decimal degrees, degrees-minutes-seconds (DMS), degrees and decimal minutes (DDM), UTM or MGRS - and writes it out in all of them at once, on the WGS 84 datum that GPS uses. Paste one coordinate, or a whole list, and copy the format your map, form or radio procedure needs.
The arithmetic runs in your browser. UTM and MGRS use the full Krüger series for the transverse Mercator projection, so a conversion and its reverse agree to well under a millimetre inside a zone.
How to use it
- Type or paste a coordinate. The reader accepts degree, minute and second symbols or plain spaces, hemisphere letters (N, S, E, W) before or after the numbers, or a minus sign for south and west.
- Check the line under the big number: it says how the input was read (for example "Degrees and decimal minutes"). If it guessed wrong, add a comma between latitude and longitude, or add the hemisphere letters.
- Copy the format you need from the table, or copy all of them. Choose how many decimal places of seconds you want; 0.01 second is about 30 cm on the ground.
- For a list, open the bulk section, paste one coordinate per line in any mix of formats, and download the result as CSV. Lines that cannot be read are kept, with the reason.
Reading the results
Decimal degrees, DMS and DDM are the same angle written three ways: 40.68925 degrees is 40 degrees and 41.355 minutes, which is 40 degrees 41 minutes 21.3 seconds. Nothing is projected, so nothing is lost.
UTM is different: it flattens the Earth onto 60 zones, each 6 degrees of longitude wide, and gives metres east and north within the zone. The band letter after the zone number tells you the 8-degree latitude band; C to M are in the southern hemisphere.
MGRS is UTM with the millions and hundred-thousands of metres replaced by a two-letter 100 km square. More digits mean a smaller square: 5 + 5 digits is 1 metre, 3 + 3 digits is 100 metres. An MGRS reference names a square, so the tool reads it as that square's south-west corner and says so.
Worked example: the Statue of Liberty from a DMS reading
A guidebook gives 40°41'21.3"N 74°2'40.2"W. Latitude is 40 + 41/60 + 21.3/3600 = 40.689250 degrees. Longitude is 74 + 2/60 + 40.2/3600 = 74.044500 degrees, negative because it is west: -74.044500.
In degrees and decimal minutes that is 40° 41.3550' N, 74° 02.6700' W (21.3 seconds is 0.355 minutes). The point lies in UTM zone 18, band T, because 74°W falls between 78°W and 72°W and 40.7°N is in the 40-48° band.
Converting back from the UTM or MGRS string returns the same latitude and longitude to within the rounding of the last digit shown, which is the check worth doing whenever you copy a coordinate by hand.
Formulas and scoring rules
- DMS to decimal
decimal = degrees + minutes / 60 + seconds / 3600Negative for S and W.- Decimal to DMS
minutes = floor(frac x 60); seconds = (frac x 60 - minutes) x 60Rounded once, on total seconds, so 59.999 seconds carries into the next minute instead of printing 60.- UTM zone
zone = floor((longitude + 180) / 6) + 1Except south-west Norway (32V is widened) and Svalbard (zones 31X, 33X, 35X, 37X).- UTM projection
Transverse Mercator, scale 0.9996 on the central meridian, false easting 500,000 m, false northing 10,000,000 m in the southKrüger n-series to sixth order on the WGS 84 ellipsoid (a = 6,378,137 m, f = 1/298.257223563).
Why the datum matters more than the format
A format converter cannot fix a coordinate taken on a different datum. GPS, web maps and this tool use WGS 84. Older national maps used local datums - OSGB36 in Britain, NAD27 in North America, ED50 in much of Europe - and the same numbers can land 100 metres or more away. If a coordinate comes from a printed map sheet, check the datum in its margin before you trust it to the metre.
Limitations: what the result does not prove
- Only WGS 84 is handled. There is no datum transformation, so coordinates from OSGB36, NAD27, ED50 or other local datums need converting with a proper transformation first.
- UTM and MGRS stop at 84°N and 80°S. The polar regions use UPS, which this tool does not produce.
- A coordinate tells you where a point is, not what is there or whether it is accessible. The map link opens OpenStreetMap only when you click it.
- Ambiguous input without separators or hemisphere letters is split in half by number count. When in doubt, add a comma or N/S and E/W.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- NGA - World Geodetic System 1984 (WGS 84) - checked 19 Sep 2026
- Karney (2011) - Transverse Mercator with an accuracy of a few nanometers, Journal of Geodesy
Frequently asked questions
How do I convert degrees, minutes and seconds to decimal degrees?
Divide the minutes by 60 and the seconds by 3,600, add both to the degrees, and make the result negative for south or west. 51° 28' 40.44" N becomes 51 + 28/60 + 40.44/3600 = 51.4779. The tool does this and shows the reverse too.
What is the difference between DMS and DDM coordinates?
Both start with whole degrees. DMS then gives whole minutes and seconds (41' 21.3"); DDM gives minutes with a decimal fraction instead (41.355'). Marine and aviation GPS units often default to DDM, while printed maps and legal descriptions often use DMS.
Why does my UTM coordinate have a letter after the zone number?
The letter is the latitude band, each 8 degrees tall, from C in the far south to X in the far north. It is not part of the maths, but it tells you the hemisphere (C to M are south) and catches the common mistake of giving a northing without saying which hemisphere it belongs to.
How precise is an MGRS grid reference?
It depends on the number of digits after the square letters. Ten digits (5 + 5) locate a 1 m square, eight digits a 10 m square, six digits 100 m and four digits 1 km. The converter shows the precision of what you enter and gives both 1 m and 100 m versions of any point.
Can I convert a whole spreadsheet of coordinates?
Yes. Paste up to 5,000 lines into the bulk section, one coordinate per line in any format, and download the CSV with latitude, longitude, DMS, UTM and MGRS columns. Rows that cannot be read are kept in the file with the reason, so nothing silently disappears.
Is a negative latitude south or north?
Negative latitude is south of the equator and negative longitude is west of Greenwich. Writing -33.8568 is the same as 33.8568 S. Use either the sign or the letter, not both - the tool refuses a minus sign combined with S or W because it is usually a copying mistake.
Last reviewed by the A2Z.Tools team against the sources listed above.
