GPS Coordinate Converter — How to Convert Between DD, DMS and DDM
Geographic coordinates are a pair of numbers that uniquely identify any point on Earth's surface: latitude (distance from the equator, ranging from −90° to +90°) and longitude (distance from the Prime Meridian, ranging from −180° to +180°). The challenge is that different industries use different formats to express the same coordinates. Web developers use Decimal Degrees, surveyors use DMS, and marine navigators prefer DDM. Our GPS coordinate converter lets you switch between all three formats instantly — no manual calculation required.
Decimal Degrees (DD) — the modern standard
Decimal Degrees is the default format for the digital world. Latitude and longitude are each expressed as a single floating-point number: 40.758896, -73.985130 for Times Square in New York. Positive latitude is north of the equator; negative is south. Positive longitude is east of Greenwich; negative is west. DD is used by Google Maps, Apple Maps, OpenStreetMap, all geocoding APIs, GeoJSON, KML, and CSV exports. To convert DD to DMS, take the integer part as degrees, multiply the decimal by 60 for minutes, then multiply the remaining decimal by 60 again for seconds.
Degrees Minutes Seconds (DMS) — the cartographic standard
Degrees Minutes Seconds is the classic format inherited from astronomy and traditional navigation. Each coordinate is divided into three parts: whole degrees (°), whole minutes (′), and decimal seconds (″). One degree contains 60 minutes; one minute contains 60 seconds. At the equator, one second of latitude equals approximately 31 meters. Example: 40°45′32.03″N, 73°59′6.47″W. DMS appears on USGS topographic maps, official geodetic surveys, military maps, and astronomical coordinate systems. To convert DMS to DD: DD = degrees + minutes÷60 + seconds÷3600.
Degrees Decimal Minutes (DDM) — the navigator's choice
Degrees Decimal Minutes sits between DD and DMS: degrees are whole numbers, minutes carry the decimal fraction, and there are no seconds. Example: 40°45.534′N, 73°59.108′W. DDM is the standard coordinate format in marine navigation — nautical charts, NOAA publications, and the US Coast Guard all use it. Aviation charts and flight planning software also rely on DDM. GPS chartplotters by Garmin, Lowrance, and Humminbird default to DDM. To convert DDM to DD: DD = degrees + decimal minutes÷60.
Coordinate precision and real-world accuracy
The number of decimal places in your coordinates directly determines their real-world accuracy. In Decimal Degrees format: 2 decimal places give roughly 1.1 km precision — enough to identify a city district. 4 decimal places reach about 11 meters — suitable for turn-by-turn navigation. 6 decimal places achieve approximately 0.1 meters — sufficient for professional surveying. When choosing a format, match it to your use case: DD for web and APIs, DDM for marine and aviation GPS devices, DMS for official maps and survey documents.