DMS to Decimal Degrees Converter

Every geographic coordinate has a latitude (north–south, −90° to 90°) and a longitude (east–west, −180° to 180°). They can be written either as decimal degrees (40.446195, −74.005974) or as degrees, minutes, and seconds (40°26'46.3"N, 74°00'21.5"W). One minute = 1/60 of a degree. One second = 1/60 of a minute = 1/3600 of a degree. The two formats describe the exact same location — just written differently.

Decimal degrees encode direction with a sign: positive latitudes are north, negative are south; positive longitudes are east, negative are west. DMS encodes direction with a letter (N, S, E, W) appended after the seconds. So 40.446195° N and +40°26'46.3" mean the same thing. When you switch between notations, convert both the magnitude and the sign/letter.

At the equator, 1 second of arc is roughly 30 m, so whole-second DMS gives ±15 m accuracy. In decimal degrees: 4 places ≈ 11 m, 5 places ≈ 1.1 m, 6 places ≈ 11 cm, 7 places ≈ 1 cm, 8 places ≈ 1 mm. Pick based on the use case — mapping apps usually accept 5–6 decimals, survey work often needs 7.

Break it into three parts: 40 degrees, 26 minutes, 46 seconds, and the hemisphere letter N (north). Degrees are the integer part; minutes are 1/60 of a degree (so there are 60 of them in one degree); seconds are 1/60 of a minute. The letter tells you the hemisphere — N or S for latitude, E or W for longitude. To check a value, verify minutes are under 60 and seconds are under 60.

N (north) and S (south) are used for latitude — the angle above or below the equator. E (east) and W (west) are used for longitude — the angle east or west of the prime meridian through Greenwich. In decimal form these letters become signs: N and E are positive, S and W are negative. So 33°51'35.9"S (Sydney latitude) equals −33.859972° in decimal.

A negative decimal means the coordinate is in the southern hemisphere (for latitude) or the western hemisphere (for longitude). Examples: São Paulo latitude is about −23.5505°; Los Angeles longitude is about −118.2437°. When you convert a negative decimal back to DMS, the result is written with an S or W letter and the magnitude is taken as positive: |−118.2437| = 118.2437 → 118°14'37.3"W.

Along a meridian (north–south), 1 arc-second ≈ 30.9 m everywhere. Along the equator, 1 arc-second of longitude ≈ 30.9 m too, but this shrinks toward the poles with the cosine of latitude — at 45° it drops to about 21.9 m, and at 60° to about 15.5 m. So when you truncate seconds to an integer, you are rounding the position by up to about 15 m on the ground near the equator and less at higher latitudes.

Most mapping services — Google Maps, OpenStreetMap, GPX files, GIS software — prefer decimal degrees with a comma or space separator: 40.446195, -74.005974. DMS is still common on printed maps, navigation charts, property deeds, and aviation. This converter lets you move freely between the two so you can paste a DMS reference into a modern mapping tool, or format a decimal reading for a report that expects DMS.