Coordinates Converter (decimal degrees, DMS & UTM)

Understanding the coordinates converter — concept and principle

This converter changes geographic coordinates between decimal degrees, degrees–minutes–seconds (DMS) and UTM (Universal Transverse Mercator) grid coordinates on the WGS 84 ellipsoid. It shows latitude and longitude in both formats, the UTM zone and latitude band, hemisphere, easting, northing and the zone's central meridian. Hikers, surveyors, GIS users and students use it to move positions between maps, GPS devices and software.

One spot, three ways to write it — with the default inputs: 52S 321424 4159641.

How it is calculated

Decimal degrees = degrees + minutes ÷ 60 + seconds ÷ 3,600 (south and west negative)
UTM zone = ⌊(longitude + 180) ÷ 6⌋ + 1; central meridian = 6 × zone − 183°
Easting and northing come from a transverse Mercator projection of WGS 84 (a = 6,378,137 m, 1/f = 298.257223563) with scale factor 0.9996 on the central meridian
False easting 500,000 m; false northing 10,000,000 m in the southern hemisphere

The projection uses Krüger's series to the fourth order, as given by Karney (2011).

The principle

DMS and decimal degrees are the same angle written two ways. UTM instead flattens the Earth into 60 strips, each 6° of longitude wide, and gives positions in metres. Within each strip a transverse Mercator projection keeps distortion small; the scale factor of 0.9996 on the central meridian spreads the error across the zone. Eastings are offset so they are always positive, and southern northings are offset so they never go negative. UTM covers 80°S to 84°N; polar regions use UPS. The special zones around Norway and Svalbard are not applied here.

Worked example

Default: 37.5665, 126.9780 (central Seoul).

Latitude 0.5665 × 60 = 33.99′ → 0.99 × 60 = 59.4″: 37° 33′ 59.40″ N.
Longitude 0.978 × 60 = 58.68′ → 0.68 × 60 = 40.8″: 126° 58′ 40.80″ E.
Zone = ⌊306.978 ÷ 6⌋ + 1 = 52; central meridian = 6 × 52 − 183 = 129°; band S; Northern hemisphere.
Projection gives easting 321,424 m and northing 4,159,641 m: 52S 321424 4159641.

How to read the result

Easting below 500,000 means the point is west of the central meridian: here about 178.6 km west of 129°E. Northing is roughly the distance from the equator along the meridian, scaled by 0.9996. Always state the datum: coordinates on a different datum can differ by tens or hundreds of metres.

Common mistakes

Swapping latitude and longitude.
Forgetting the minus sign for south or west.
Mixing coordinates from different datums.
Using a UTM position with the wrong zone or hemisphere.

Keep in mind: Results assume WGS 84. For legal surveys or navigation, use the official datum and certified tools for your country.

Frequently asked questions

How do I convert DMS to decimal degrees?

Add degrees + minutes ÷ 60 + seconds ÷ 3,600, and make the result negative for south or west.

What UTM zone is Korea in?

Most of South Korea lies in zones 51 and 52; Seoul is in zone 52.

Why is easting 500,000 at the central meridian?

A false easting of 500,000 m keeps all eastings in a zone positive.

Sources: C. F. F. Karney, "Transverse Mercator with an accuracy of a few nanometers", Journal of Geodesy 85(8):475–485 (2011) · J. W. Hager, J. F. Behensky, B. W. Drew, The Universal Grids: UTM and UPS, DMA Technical Manual 8358.2 (1989) · NGA, World Geodetic System 1984

Checked 9 Nov 2026. Karney C. F. F. (2011), “Transverse Mercator with an accuracy of a few nanometers”, Journal of Geodesy 85(8):475–485 (Krüger series, coefficients α₁–α₄ and β₁–β₄, conformal latitude and its Newton inversion); Hager J. W., Behensky J. F., Drew B. W., The Universal Grids: UTM and UPS, DMA Technical Manual 8358.2 (Defense Mapping Agency, 1989) — 6° zones, k₀ = 0.9996, false easting 500,000 m, false northing 10,000,000 m south, 80°S–84°N limits; WGS 84 defining parameters from NGA, World Geodetic System 1984.

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