DMS ↔ Decimal Coordinate Converter

Overview

The DMS to Decimal Coordinate Converter translates latitude and longitude between three common notations: decimal degrees (DD), degrees and decimal minutes (DDM), and degrees minutes seconds (DMS). Type a coordinate in any of the three formats and the tool returns the other two, with the correct hemisphere sign baked in.

Different industries entrench different formats. Web maps and GeoJSON use signed decimal degrees. Aviation and marine charts favour degrees and decimal minutes (51° 28.665' N). Survey reports, historical documents and many GPS receiver displays use full DMS with seconds (51° 28' 39.9" N). Manually switching between them is fiddly because the minute and second components share names with time units and the hemisphere letter has to be tracked separately from the sign.

How it works

Decimal degrees encode the hemisphere in the sign of the value: positive for North or East, negative for South or West. To convert decimal degrees D into DMS, take the integer degrees as floor(|D|), multiply the fractional part by 60 to get the minutes, then multiply the remainder by 60 again to get the seconds. The hemisphere letter (N/S for latitude, E/W for longitude) is added based on the original sign.

To go the other way, the tool parses the degree, minute and second components and recombines them as D + M/60 + S/3600, multiplied by -1 if the hemisphere is S or W. The parser is forgiving about whitespace, degree signs, primes ('), double primes ("), and the common substitutes deg, m, s.

Examples

• 51.4769 (decimal degrees) becomes 51° 28' 36.84" N (DMS) or 51° 28.6140' N (DDM) - Greenwich Observatory's latitude.
• -118.2437 (decimal) becomes 118° 14' 37.32" W - Los Angeles longitude.
• 40° 26' 46" N (DMS) parses back to 40.4461 decimal.
• 33° 51.6' S (DDM) parses to -33.86 decimal - Sydney latitude.

FAQ

What are the standard symbols?
A degree sign °, a single prime ' for minutes, and a double prime " for seconds. The tool also accepts plain text - 40 26 46 N is valid input.

Which format should I store coordinates in?
Decimal degrees are the safest storage format. They are unambiguous, sort correctly, and need no string parsing. Convert to DMS or DDM only for human display.

Can the tool handle negative DMS?
DMS itself does not use negative numbers; sign is expressed by the hemisphere letter. The tool will refuse -51° 28' 36" N as ambiguous; use 51° 28' 36" S instead.

How precise is one second of arc?
At the equator, one second of latitude is about 31 metres on the ground. Seconds of longitude shrink as you move toward the poles; at 60 degrees latitude, one second of longitude is about 15 metres.

Try DMS ↔ Decimal Coordinate Converter