What is the difference between EPSG:4326 and EPSG:3857?

4326 is plain WGS84 latitude and longitude in degrees. 3857 is the Web Mercator projection of those coordinates onto a square plane measured in metres, which is what tile-based maps and most web mapping libraries work in internally.

Why does Web Mercator stop at 85 degrees?

Because the projection runs to infinity at the poles. Cutting it at 85.0511287° makes the projected world exactly as tall as it is wide, which is what lets the map be divided into a neat quadtree of square tiles.

Is Web Mercator the same as the old EPSG:900913 code?

Yes — 900913 was an unofficial code coined before the projection was formally registered, and 3857 is the official identifier. You may also still see 102100 and 3785 for the same thing.

Can I measure area in Web Mercator metres?

Not reliably. The scale factor grows with latitude, so an area computed on the projected plane is inflated by roughly the square of that factor. Measure on the sphere or in a local equal-area projection instead.

What does ground resolution mean on a map tile?

How many metres of real ground one screen pixel covers at a given zoom. It is about 156 km per pixel at zoom 0 and halves with each level, scaled by the cosine of the latitude.

Web Mercator Converter

Convert latitude and longitude to Web Mercator metres and back, with scale and resolution at any zoom.

The Web Mercator Converter runs entirely in your browser. Coordinates are projected on your device and never sent to a server.

Work out map tiles

About Web Mercator Converter

Web Mercator is the projection behind almost every slippy map, and the coordinates it uses are metres on a sphere rather than degrees on an ellipsoid. Moving between the two is a pair of short formulas, but they are the sort that get typed in wrong at two in the morning, and a sign error puts a marker in the wrong hemisphere. This converter runs them in both directions on a whole list of coordinates at once. It also reports the two figures that decide how a map actually looks: the scale distortion at your latitude, which is why Greenland looks continental, and the ground resolution in metres per pixel at each zoom level.

Features

Converts WGS84 degrees to EPSG:3857 metres and back, line by line
Handles a whole list at once, with per-line error messages
Scale distortion factor at the latitude you entered
Ground resolution in metres per pixel at any zoom level
Global pixel coordinates on the 256-pixel tile grid
Swaps direction and reuses the output as the next input
CSV export with latitude, longitude, x and y side by side

How to use the Web Mercator Converter

Choose the direction: degrees to metres, or metres back to degrees
Paste your coordinates, one pair per line
Read the converted values and copy or download them as CSV
Set a zoom level to see the ground resolution and pixel position there

Example

Input

51.5074, -0.1278

Output

-14226.631, 6711542.476

London in EPSG:3857 metres — x from longitude, y from the logarithmic latitude term.

Common errors & troubleshooting

The y value comes out as infinity near the poles. — Web Mercator cannot represent them. Latitudes are clamped to ±85.0511°, the cutoff that makes the projected world square, which is why web maps stop short of the poles.
Coordinates land in the wrong place on the map. — Check the order. Degrees are read latitude first here, matching how people write them, while the metre pairs are x then y — the reverse convention.
Distances measured in EPSG:3857 look too long. — They will be, away from the equator. Mercator stretches by 1/cos(latitude), so a metre on the projected plane in London represents about 0.62 metres on the ground.
The results differ slightly from a GIS package. — Some tools project onto the WGS84 ellipsoid rather than the sphere Web Mercator defines. The spherical form used here is what EPSG:3857 specifies, and what tile servers assume.

Frequently asked questions

What is the difference between EPSG:4326 and EPSG:3857?: 4326 is plain WGS84 latitude and longitude in degrees. 3857 is the Web Mercator projection of those coordinates onto a square plane measured in metres, which is what tile-based maps and most web mapping libraries work in internally.
Why does Web Mercator stop at 85 degrees?: Because the projection runs to infinity at the poles. Cutting it at 85.0511287° makes the projected world exactly as tall as it is wide, which is what lets the map be divided into a neat quadtree of square tiles.
Is Web Mercator the same as the old EPSG:900913 code?: Yes — 900913 was an unofficial code coined before the projection was formally registered, and 3857 is the official identifier. You may also still see 102100 and 3785 for the same thing.
Can I measure area in Web Mercator metres?: Not reliably. The scale factor grows with latitude, so an area computed on the projected plane is inflated by roughly the square of that factor. Measure on the sphere or in a local equal-area projection instead.
What does ground resolution mean on a map tile?: How many metres of real ground one screen pixel covers at a given zoom. It is about 156 km per pixel at zoom 0 and halves with each level, scaled by the cosine of the latitude.

Related tools

Map Tile Calculator — Convert between coordinates, XYZ tiles, TMS and quadkeys, with tile counts.
Coordinate Converter (DMS & Decimal) — Convert coordinates between decimal degrees, DMS and degrees-decimal-minutes, both ways, in your browser.
UTM Converter — Convert between latitude/longitude and UTM coordinates (zone, hemisphere, easting, northing) on the WGS84 ellipsoid.
Distance Between Coordinates — Measure the great-circle distance between two latitude/longitude points in km, miles and nautical miles, with bearing and a map.
GeoJSON Bounding Box — Get the bounding box, centre, area and length of any GeoJSON, in both coordinate orders.
Geohash Converter — Encode latitude/longitude to a geohash and decode a geohash back to coordinates, with bounding box and neighbors.