EPSG:4326 is in degrees - 3D sphere Bounds: -180.0 -90.0 180.0 90.0 EPSG:3857 is in metres - 2D projection Bounds: -20037508.34 -20048966.1 20037508.34 20048966.1 Example: A) Lat(48.8589506) Lon(2.2768485) B) Lat(6250962.06) Lon(253457.62) Source: https://gis.stackexchange.com/a/380296