UTM to Lat-Long Converter

How it is calculated

The tool reverses the Transverse Mercator projection on the WGS84 ellipsoid (a = 6378137 m, flattening 1/298.257223563) with the UTM scale factor 0.9996. It subtracts the false easting of 500,000 m to get the distance x from the zone's central meridian, and subtracts the 10,000,000 m false northing for the southern hemisphere. The northing is divided by 0.9996 to give the meridian arc length, from which the footpoint latitude is found, and standard series terms then yield latitude and longitude. The longitude is the zone's central meridian, (zone − 1) × 6 − 180 + 3 degrees, plus the offset. Results are decimal degrees with six decimals (negative = south or west). Zone must be 1 to 60, easting 100,000 to 900,000, northing 0 to 9,400,000 (north) or 1,100,000 to 10,000,000 (south); outside these, no result. A hemisphere beginning with N or S is accepted, and an empty field means N. Latitude band letters (such as T) are not accepted.

Common mistakes

• Entering a latitude band letter such as T from 18T as the hemisphere. Only N or S works: band letters C to M are southern and N to X northern, so for 18T enter N. The letter T itself gives no result.
• Choosing S for a northern location. The same numbers with hemisphere S in zone 18 move the point to latitude −49.579049°, thousands of kilometres from the intended place.
• Swapping easting and northing. Easting is the 6-digit number near 500,000 and northing the 7-digit one; swapped values are out of range and return no result.
• Using the wrong zone. Every zone is 6° wide, so zone 19 with the same easting and northing gives longitude −68.005970° instead of −74.005970°.
• Assuming a different datum. The tool assumes WGS84; coordinates from an older NAD27 or ED50 grid can differ by tens or hundreds of metres.