Work out utm coordinate conversion instantly with clear inputs, formula shown and shareable results.
UTM divides the world into 60 six-degree zones numbered eastward from the antimeridian, each with its own transverse Mercator projection centred on a meridian at zone middle. London at -0.128 degrees falls in zone 30, central meridian -3, band U. Easting is measured from a 500,000 m false origin at that meridian with a 0.9996 scale factor.
Zone number
zone = floor((longitude + 180) / 6) + 1
Central meridian
CM = (zone - 1) x 6 - 180 + 3
So that eastings stay positive across the whole zone. A zone is about 668 km wide at the equator, so the offset covers the western half.
Because Mercator distortion becomes unacceptable near the poles. UPS, a polar stereographic projection, is used beyond.