What this calculator does
DDM stands for degrees decimal minutes, a coordinate format written as a whole number of degrees followed by minutes expressed as a decimal, such as 37 degrees 48.816 minutes. It sits between two other common formats: plain decimal degrees, which is a single decimal number like -37.8136, and degrees minutes seconds (DMS), which splits the fractional part further into whole minutes plus decimal seconds. Marine GPS units and many aviation charts display coordinates in DDM by default, so converting between it and decimal degrees is a routine step when moving a position between a chartplotter, a mapping app and a spreadsheet.
The conversion itself is simple arithmetic once the direction is clear. Going from decimal degrees to DDM, the whole-number part becomes the degrees and the leftover fraction is multiplied by 60 to give decimal minutes. Going the other way, the minutes are divided by 60 and added back onto the degrees, with the sign of the original degrees value carried through to the result. The one place people slip up is applying the sign twice, once to the degrees and again to the minutes, which flips the answer to the wrong hemisphere.
The formula
For decimal degrees to DDM: take the absolute value of the decimal degrees, the whole-number part is the degrees, and the remaining fraction multiplied by 60 gives the decimal minutes, with the original sign (north/south or east/west) applied only once, to the degrees. For DDM to decimal degrees: divide the minutes by 60, add the result to the absolute value of the degrees, then reapply the sign of the entered degrees.
| Term | Meaning |
|---|---|
| DDM | Degrees decimal minutes, a coordinate written as whole degrees plus minutes expressed as a decimal, e.g. 37 deg 48.816 minutes. |
| Decimal degrees | A coordinate as a single signed decimal number, e.g. -37.8136, the format most mapping APIs use internally. |
| Decimal minutes | The fractional part of a degree, expressed out of 60 rather than as a further decimal degree. |
The inputs explained
| Field | What to enter |
|---|---|
| Direction | Choose whether you are converting a decimal degree value into DDM, or a DDM pair back into decimal degrees. |
| Decimal degrees | A coordinate in plain decimal degrees, negative for south or west. |
| Degrees | The whole-number degrees part of a DDM coordinate, keep the sign here (negative for south or west). |
| Decimal minutes | The decimal minutes part of a DDM coordinate, always entered as a positive number between 0 and 60. |
When to use it
Reading a chartplotter or GPS display
Marine and aviation GPS units commonly show position in DDM. Converting that reading to decimal degrees makes it usable in a mapping tool or spreadsheet that expects a single decimal number per axis.
Entering coordinates from a paper chart
Nautical charts and some survey documents list latitude and longitude in degrees and decimal minutes. Converting to decimal degrees first avoids manual arithmetic errors when plotting the point elsewhere.
Formatting coordinates for a device that expects DDM
Some older GPS units and logging formats only accept DDM input. Converting a decimal-degree coordinate pulled from a map into DDM gets it into the format the device needs.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Converting decimal degrees to DDM
A range of decimal degree values converted to the DDM format.
| Decimal degrees | DDM coordinate |
|---|---|
| -37.8136 deg | -37° 48.816′ |
| 40.7128 deg | 40° 42.768′ |
| -33.8688 deg | -33° 52.128′ |
| 51.5072 deg | 51° 30.432′ |
| 35.6762 deg | 35° 40.572′ |
Converting DDM back to decimal degrees
A fixed 37 degrees, with a range of decimal minute values, converted back to decimal degrees.
Questions
What is the difference between DDM and DMS?
DDM (degrees decimal minutes) splits a coordinate into whole degrees and decimal minutes, such as 37 deg 48.816 minutes. DMS (degrees minutes seconds) splits it a level further into whole degrees, whole minutes and decimal seconds, such as 37 deg 48 minutes 57.6 seconds. Both describe the same position, just with a different level of subdivision.
Which format does Google Maps or GPS coordinates normally use?
Most web mapping tools and APIs, including Google Maps search, expect plain decimal degrees, a single signed decimal number per axis. DDM and DMS are more common on dedicated GPS, marine and aviation equipment, and need converting before pasting into a decimal-degree field.
How do I know which hemisphere a DDM coordinate is in?
The sign or letter suffix on the degrees value carries the hemisphere: a negative degrees value, or a S or W suffix, means south or west. The minutes value itself is always entered and read as positive, regardless of hemisphere.
Can decimal minutes ever reach exactly 60?
No, by convention decimal minutes stay in the range 0 up to but not including 60. A value of 60 minutes is instead carried over as one additional whole degree, so 37 deg 60.0 minutes is written as 38 deg 0.0 minutes.
For a coordinate given with whole minutes and seconds instead of decimal minutes, see the degrees, minutes, seconds converter.