Coordinate Converter
Convert between WGS84 lat/lon, Korean TM belts (EPSG:5185-5188), UTM-K 5179, UTM zones and the legacy Bessel datum, with DMS and DDM display and a map preview.
Converts to
Height (orthometric ↔ ellipsoidal)
Ellipsoidal (GPS): 23.097 m · Geoid N = 23.097 m
Kept points
A point you keep stays in this list until you leave the page — nothing is saved or sent. Up to 1000.
The map is off until you open it; when open it loads OpenStreetMap tiles for the area around your point, so OpenStreetMap can see roughly where you are looking. The numbers you type are not sent.
Many points at once
One point per line: Longitude, then Latitude, in the input system above — separated by a comma, tab, semicolon or spaces. Up to 1000 lines.
Another coordinate system
Convert coordinates between systems
Pick your input coordinate system, enter the values, and every other system is computed at once — copy any line. Supports WGS84 (GPS) longitude/latitude, the Korean 2000 Transverse-Mercator belts (EPSG:5185 West, 5186 Central, 5187 East, 5188 East Sea), the UTM-K unified grid (EPSG:5179, used by Naver and Kakao maps), UTM zones 51N/52N, and the legacy Korea 1985 Bessel central belt (EPSG:5174). Latitude/longitude also shows in degrees-minutes-seconds and in degrees and decimal minutes (DDM), and can be typed in either. An MGRS / USNG row gives the grid reference too, and a system that is not in the list can be added by pasting its proj4 string or WKT — epsg.io prints both under every code — into Another coordinate system, after which it joins the input list and the results. Or paste a whole point takes a point as it is copied: a latitude, longitude pair from a map app, a degrees-minutes-seconds pair, an MGRS reference, or two metre values in a projected system; and clicking the open map moves the point there. Many points at once converts a pasted list or an opened CSV, one point per line, into a CSV to copy or download. Points kept with Keep this point are measured too: the length of the path through them and the area they enclose.
How accurate is it?
Conversions use proj4 with standard EPSG definitions, cross-checked against an independent Transverse-Mercator implementation for the Korean belts (agreement within 1 mm). Systems on the GRS80/WGS84 datum (5185–5188, 5179, UTM) are exact; the legacy Bessel belt (5174) uses a 7-parameter datum shift and is approximate to about ±1–2 m, since Korea officially uses an NTv2 grid for that transform.
Is anything uploaded?
No. All coordinate math runs locally in your browser. The map is off until you open it; when open it loads OpenStreetMap tiles for the area around your point, so OpenStreetMap can see roughly where you are looking. The numbers you type are not sent.
Frequently asked questions
Is anything uploaded?
No. All conversions run in your browser. The map is off until you press Show map; once open it loads OpenStreetMap tiles for the area around your point, so OpenStreetMap can see roughly where you are looking.
Which coordinate systems are supported?
WGS84 lon/lat, Korean 2000 TM belts (EPSG:5185/5186/5187/5188), UTM-K unified (EPSG:5179), UTM 51N/52N (EPSG:32651/32652) and legacy Bessel EPSG:5174, plus degrees↔DMS and DDM. MGRS / USNG references are shown and read too, and any other system can be added by pasting its proj4 string or WKT into “Another coordinate system”.
What is EPSG:5186?
The Korea 2000 / Central Belt Transverse-Mercator system (central meridian 127°E) — the national grid most used for survey and construction in central Korea.
How accurate is the legacy Bessel (5174) conversion?
It uses a 7-parameter datum shift and is accurate to roughly ±1–2 m across the country; the modern GRS80 systems are exact.
Can I use a coordinate system that is not in the list, or convert many points at once?
Yes to both. Paste the system’s proj4 string or WKT — epsg.io prints both under every code — into “Another coordinate system”, and it joins the input list and the results as “Your system” and travels in the page link. “Many points at once” takes one point per line, pasted or from “Open CSV…”, converts them to any other system or to MGRS, and hands back a CSV to copy or download; a line it cannot read keeps its row with the answer left blank and is named.
Can I enter DDM, swap the two boxes, or save points as KML or DXF?
Yes. For WGS84, a DDM button beside Decimal and DMS takes degrees and decimal minutes, and the WGS84 result prints a DDM line under its DMS one. “Swap the two boxes” exchanges the two values in one press, for a latitude-first pair pasted the wrong way round. “Keep this point” adds the point to a “Kept points” list, where each can be reopened or removed; the list lasts until you leave the page. The kept points download as KML, GeoJSON, CSV or DXF, with the CSV and DXF in the system you pick under “CSV and DXF coordinates in”. Tick “Add the height to each result and each kept point (X, Y, H)” and the height you entered is printed in every result row with its kind, and each row’s Copy gives X, Y, H.
Can it measure the points I keep?
Yes. Once the “Kept points” list holds more than one point, it gives the length of the path through them, point to point in the order kept, and, once they enclose a shape, the area closed back to the first point, in m² or km² with hectares beside it. Both are measured on the WGS84 ellipsoid; for an area, keep the points in order round the edge.