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What Is Longitude?

Longitude is the angular distance east or west of the prime meridian in Greenwich. It ranges from −180° to +180° (or 180° W to 180° E). Unlike latitude, the ground distance of one degree of longitude shrinks toward the poles.

Meridians meet at the poles

Lines of equal longitude are meridians. They are farthest apart at the equator (about 111 km per degree) and meet at the poles. That is why a longitude-only offset is a poor distance estimate at high latitudes; use a geodesic or the distance tool instead.

Longitude and civil time

Earth rotates 15° of longitude per hour, which is the historical basis of time zones. Modern civil time uses IANA zones and political borders, so two places with similar longitude can still use different clocks. CoordMap city pages show both the WGS84 longitude and the IANA identifier.

Sign convention

CoordMap uses signed decimal degrees: negative longitude is west of Greenwich, positive is east. DMS strings use E/W letters instead. The date line near ±180° is a special case; crossing it changes the calendar date, not the coordinate system.

Examples

Prime meridian0°
New York (approx.)74.0060° W
Tokyo (approx.)139.6503° E

Use the matching CoordMap tool

Related tools

Longitude and Latitude FinderFind longitude and latitude from an address, or get the address from the maptime-zonesWorld time zones with current time, UTC offsets and detailed explanationsMeasure DistanceMeasure how far two places are from each otherConvert FormatsSwitch between decimal lat/lng and degrees-minutes-seconds

Related guides

What Is Latitude?Latitude is the angular distance north or south of the equator. It ranges from 90° S at the South Pole to 90° N at the North Pole, with 0° on the equator. On CoordMap and in GPS, latitude is listed first in a WGS84 pair.Latitude vs LongitudeLatitude is north–south (−90 to 90). Longitude is east–west (−180 to 180). CoordMap writes latitude first. If a “latitude” is 120, the pair is almost certainly swapped or in the wrong CRS.How to Read GPS CoordinatesGPS coordinates on CoordMap are WGS84. Decimal degrees (DD) look like 51.5074. DMS splits each value into degrees, minutes and seconds with N/S or E/W. DDM uses degrees plus decimal minutes. All three can describe the same point.

Common questions

Why is one degree of longitude not a fixed distance?

Meridians converge toward the poles, so the east–west ground distance of 1° shrinks with the cosine of latitude.

Does longitude determine my time zone?

It is a useful hint, not a rule. Use the IANA zone on the city or time-zone page; offsets change with daylight saving.