Zerdly

DMS to DDM Converter

Converts coordinates from degrees minutes seconds to degrees decimal minutes.

100% FreeRuns in your browserBasic
How to use this calculator
DMS value

Overrides the boxes, e.g. 40°26′46.302″

Display only — the exact value is carried, and a rounded 60 carries into the next unit.

Result

Enter a value to see it converted.

More decimals describe the notation more finely; they do not make the coordinate more accurate than the measurement behind it.

Which way is positive
Teaching diagram
Which way is positiveA globe outline split by the equator and the prime meridian: north and east are positive, south and west negative.N +S −E +W −Latitude: N +, S −Longitude: E +, W −−33.8 (latitude) = 33.8° S−0° 30′ = 0° 30′ S−33.8 N says two things:you choose which to trust
North and east are positive; south and west are negative. The sign (or letter) applies once to the whole angle, so −0° 30′ is 0° 30′ S on latitude — the hemisphere survives a zero degree value.

How the method works

A fixed worked example to explain the method — it is not your result.

One angle, three representations
Illustrative method
One angle, three representationsThe same angle written as degrees-minutes-seconds, degrees and decimal minutes, and decimal degrees, with the conversion between each.DMS40°26′46.302″DDM40°26.7717′DD40.446195°26′ + 46.302″ ÷ 60= 26.7717′40° + 26.7717′ ÷ 60= 40.446195°
40° 26′ 46.302″ = 40° 26.7717′ = 40.446195°. Seconds ÷ 60 join the minutes; minutes ÷ 60 join the degrees. The sign (or hemisphere letter) applies once to the whole angle.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Choose Single angle, Latitude & longitude, or Batch / CSV.
  2. Pick the angle type: a plain signed angle, a latitude (N/S) or a longitude (E/W).
  3. Type degrees, minutes and seconds in the boxes — or paste the whole value, e.g. 40°26′46.302″ N.
  4. Choose how many decimals of minutes to show (0–10). The result updates as you type; copy the DDM, the decimal degrees or the whole pair.

How it works

Decimal minutes = minutes + seconds ÷ 60, and the degrees stay the same. The sign or hemisphere applies to the whole value, so 0° 30′ 0″ S is −0.5°, not +0.5°.

The value is held as an exact fraction and rounded once, at display. A rounded 60 carries into the degrees: 12° 59′ 59.9999″ at three decimals is 13° 0.000′, never 12° 60.000′.

Minutes and seconds must be at least 0 and less than 60. A latitude of exactly 90° (or a longitude of 180°) cannot have any minutes or seconds.

Batch mode reads one pair per line, reports each rejected row with its reason, and downloads a CSV of every row or of the valid rows only.

Worked example

40° 26′ 46.302″. = 40° 26.7717′ (26 + 46.302 ÷ 60 = 26.7717 minutes) = 40.446195°.

Common mistakes

  • Writing a minus on the degrees only. −0° 30′ is −0.5°, and a hemisphere letter does the same job.
  • Treating more minute decimals as more accuracy. The notation becomes finer; the measurement behind it does not.
  • Rounding the minutes to 60 by hand instead of carrying it into the degrees.

Frequently asked questions

Do I lose precision converting between formats?

No — all three formats describe the same angle. Only the on-screen rounding changes, and it is applied once to the exact value.

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Cite this tool

Zerdly. (2026). DMS to DDM Converter. Retrieved from https://www.zerdly.com/tools/dms-to-ddm-converter/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.