UTM grid zones explained

The Universal Transverse Mercator (UTM) grid cuts the Earth into 60 zones, each 6° of longitude wide, and gives any position as meters east and north inside its zone. A UTM coordinate looks like 10T 548894 E 5274326 N: the Space Needle in Seattle.

See the UTM grid on the globe Convert coordinates

The zone number

Zones are numbered 1 to 60 from the date line eastward: zone 1 covers 180°W to 174°W, zone 31 covers 0° to 6°E, zone 60 ends at 180°E. To find a zone from a longitude, add 180, divide by 6, round down and add 1. Seattle at 122°W: (−122 + 180) ÷ 6 = 9.67, so zone 10. Each zone has its own map projection, a Transverse Mercator centered on the zone's middle meridian, which keeps distances true to within about 0.1% across the zone: 0.04% short along its middle meridian, about 0.1% long at its edges near the equator.

The letter after it

The letter is a band of latitude 8° tall, from C at 80°S to X at 72°N (X is 12° tall, up to 84°N); I and O are skipped. It tells you which hemisphere a northing belongs to: C to M lie south of the equator, N to X north. Some software writes a plain N or S instead of the band letter: 10N 548894 5274326 says the same as 10T 548894 5274326. Grid Globe writes the band letter in its UTM and MGRS lines alike, and reads either form when you type one.

Easting and northing

• Easting is meters east of the zone's central meridian plus 500,000, so it is never negative: the central meridian is 500,000 and the zone's edges are near 166,000 and 834,000 at the equator, closer together toward the poles.
• Northing is meters north of the equator. South of the equator 10,000,000 is added, so a northing counts up from the South Pole's neighborhood instead of going negative: Sydney's Opera House is 56H 334900 E 6252288 N.

Write the easting first, then the northing, both in whole meters.

The lines on the globe

Choose UTM on the globe and the grid is drawn in each zone's own projection: the zone boundaries from space, then lines every 100 km, 10 km, 1 km and 100 m as you fly down, each labeled with its full easting or northing. Where a zone meets its neighbor the two grids meet at an angle, because each zone's north is its own central meridian's north. Switch to MGRS and the same lines carry letters instead: What MGRS is.

The exceptions

• Zone 32 over Norway is widened to begin at 3°E between 56°N and 64°N, so southern Norway sits in one zone; zone 31 is 3° wide there.
• Svalbard, between 72°N and 84°N, has four zones, 31, 33, 35 and 37: 31 and 37 are 9° wide, 33 and 35 are 12°; zones 32, 34 and 36 are missing.
• The poles: beyond 84°N and 80°S the UPS (Universal Polar Stereographic) grid takes over, written with a polar zone letter, A or B in the south, Y or Z in the north, then meters east and north of a point 2,000 km west and 2,000 km south of the pole on the grid, so the pole itself is 2000000 E 2000000 N: Z 2425425 E 1530820 N. Grid Globe reads and draws it, and shows it in the UTM line's place over the caps.

Try it on the globe

• The 60 zones from space
• Where zones 10 and 11 meet, at 120°W across Washington State, and the grids meet at an angle
• The widened zone 32 over Norway
• Svalbard's four zones

Used Google Earth Pro's UTM grid? MGRS and UTM grids without Google Earth Pro shows where its settings are here.