EPSG Code Lookup

Search the registry

Showing 486 of 486 codes.

Click any row to see its projection method and parameters. Search matches the code, the name and the area of use, so Ohio, 32617 and UK all work.

What an EPSG code actually identifies

An EPSG code is a short number that names one entry in the EPSG Geodetic Parameter Dataset — the registry of coordinate reference systems, datums, ellipsoids, units and transformations maintained by the IOGP. The registry grew out of the European Petroleum Survey Group, which is where the four letters come from, and it is now the common language that GIS software, GNSS receivers, web services and survey instruments use to say which coordinates they mean.

A code is written as authority:code, so EPSG:4326 is latitude and longitude on WGS 84 and EPSG:32617 is WGS 84 / UTM zone 17N. Because a code identifies a complete system rather than a place, the same field on the ground can honestly be described by several different codes at once: the position is the same, the numbers attached to it are not.

The important consequence is that a coordinate pair is meaningless until you know its code. The pair 630084.301, 4833438.586 is a perfectly good position in UTM zone 17N, and a position in the middle of the Atlantic if you read it as anything else.

The four kinds of code

Almost everything you will meet falls into one of four groups, and the group tells you what the numbers look like before you open the file.

A compound code bolts a horizontal and a vertical system together — a State Plane zone with NAVD88 heights, for instance — which is what a set of survey observations usually is. The relationship between the ellipsoidal height in a 3D code and the elevation in a vertical code is the geoid, which is covered in geoid vs ellipsoid.

The codes you will meet most often

If you only ever memorise a dozen numbers, these are the dozen.

For any UTM zone the arithmetic is regular, which is why the block is worth remembering: the code for zone n north is 32600 + n and for zone n south it is 32700 + n. The corresponding zone is worked out from the longitude, as explained in how to read UTM coordinates.

4326 or 3857? The pair that catches everyone

These two codes cover most of the world's data and they are constantly confused, because both carry the words WGS 84. They are not the same kind of thing at all. 4326 is geographic — degrees of latitude and longitude. 3857 is projected — metres of easting and northing, with the equator and the prime meridian at the origin.

There is a second trap inside 3857. A true Mercator projection carries the ellipsoid onto the plane, but Pseudo-Mercator replaces the ellipsoid with a sphere of radius 6,378,137 m. That makes the arithmetic simpler and the tiles square, and it also means the northings are systematically different from a genuine ellipsoidal Mercator such as 3395.

So the two are about 21 km apart in northing at 30° of latitude and 37 km apart at 60°. Neither is wrong — they answer different questions. But if a file says 3857 and was actually computed on the ellipsoid, or the other way round, a kilometre-scale disagreement appears that no amount of re-checking the survey will explain.

Pseudo-Mercator also inflates distance and area away from the equator: a scale factor of about 1.15 at 30°, 1.41 at 45° and 2.0 at 60°. Never measure area or distance on a Web Mercator layer. Use a projected zone such as a State Plane or UTM zone instead, or convert to latitude and longitude and work on the ellipsoid.

Codes that look alike but are not

Most coordinate mix-ups are not typos. They are two codes that differ by a plausible-looking amount.

How to find the code for an area you have never worked in

1. Ask what the coordinates are for. A national mapping agency will have a national grid; a state or province will often have its own zone; a project tied to a global data set will be in UTM. The purpose narrows the list faster than any search.
2. Look for the datum in the metadata. WGS 84, NAD83, ETRS89, GDA2020, CGCS2000 and NAD27 each lead to a different family of codes, and the difference is usually stated somewhere in the file header, the service capabilities document or the drawing title block.
3. Check the unit. Metres and feet split every family in two. If a northing is around 5,000,000 in metres it is a UTM-type coordinate; if it is around 16,000,000 it is probably feet, or a national grid with its own origin.
4. Read the order of magnitude of the easting. About 500,000 means a UTM-type zone centred on a meridian. A six-figure easting in the 100,000s with a small northing means a local grid with its own false origin.
5. Search the area name here. Type the state, country or zone name into the box above and the candidates appear with their units and areas of use, which is usually enough to identify the one that matches the extent of your data.
6. Confirm with a known point. Convert one coordinate you can verify independently — a survey mark, a monument, a well-known landmark — and check that it lands where it should. One confirmed point is worth more than any amount of reading.

EPSG codes and Esri WKIDs

Esri software uses its own well-known identifiers alongside the EPSG ones. Many are identical — Esri also calls the British National Grid 27700 — but a substantial number are not, and the two registers do not always describe the same thing under the same number.

• Web Mercator. Esri:102100 and its predecessor Esri:102113 both describe what EPSG calls 3857. A service quoting 102100 is quoting the same projection under a different authority.
• North American State Plane. Esri assigns codes in the 102000s to State Plane zones whose EPSG equivalents sit in the 2200s and 26900s, so 102603 and 2205 can describe the same Kentucky zone in different registers.
• Deprecated entries. Both registers retire codes. A code that still works in one package may already be flagged as deprecated in the registry, which is why it is worth checking a definition rather than trusting a number that has always been in the file.

When two systems disagree, the safest course is to send the full definition — the WKT or the PROJ string — rather than a number, because a number means nothing without its authority.

Further reading

Related calculators and converters

Frequently asked questions