How this calculation works
Change coordinate notation while preserving the supplied angular position. DMS display rounds seconds to three decimal places with carry; decimal output retains up to nine display places. No datum or projection transformation is performed.
Magnitude = degrees + minutes/60 + seconds/3600; south and west use negative decimal signsA worked example
12.9716° N, 77.5946° E becomes 12° 58′ 17.760″ N and 77° 35′ 40.560″ E. The DMS input components recover the same decimal coordinates.
Good to know
Notation only, not geolocation, a map, UTM conversion, datum/epoch transformation or survey correction. Latitude magnitude ≤90° and longitude ≤180°; minutes/seconds must be zero at those limits. Zero coordinates normalize to N/E. Rounded DMS display does not add precision to the original measurement.
Reference: NOAA NGS: coordinate formats and degrees/minutes/seconds relationship (opens in a new tab) ↗
Check the land-unit definitions and sources
The standard factors use the international foot and an acre of 43,560 sq ft. Cent means 1/100 acre; gunta means 1/40 acre; the selected Chennai ground means 2,400 sq ft.
The Assam report defines bigha as 14,400 sq ft, katha as 2,880 sq ft and lecha as 144 sq ft. The cited West Bengal court order mentions a 720-sq-ft katha convention. These are explicit presets, not an automatic definition for every record or every place using the same name. Match your record to the stated convention, or use its verified custom factor.
- NIST: exact international-foot and acre factors (opens in a new tab) ↗
- API Setu MDDS: acre/cent and acre/gunta relationships (opens in a new tab) ↗
- Greater Chennai Corporation: one ground is 2,400 sq ft (opens in a new tab) ↗
- Government of Assam AIRBMP framework: section 7.2, page 28 (bigha, katha and lecha) (opens in a new tab) ↗
- Supreme Court order, 7 May 2025: paragraph 2, page 2 (West Bengal katha) (opens in a new tab) ↗
The acre relationships are converted using exact base factors. Rounded or unrelated regional values in a reference table are not substituted for these definitions.
A coordinate changes its notation, not its reference frame
Decimal latitude 12.9716 means 12 whole degrees plus 0.9716 of a degree. Multiplying the fractional degree by 60 gives 58.296 minutes; the remaining 0.296 minute gives 17.76 seconds. Longitude 77.5946 similarly becomes 77° 35′ 40.560″.
The decimal 12.3015 is not shorthand for 12 degrees, 30 minutes, 15 seconds. Those components instead represent 12 + 30/60 + 15/3600, approximately 12.504167 decimal degrees. Component mode asks for separate fields so packed notation is not silently guessed.
This page performs neither a datum transformation nor a projection. A number written in degrees is not converted into a metre-based survey point by changing its typography. Measured plot area needs actual horizontal lengths or appropriate planar coordinates.
Hemisphere and display rounding need explicit conventions
North and east are positive here; south and west are negative. Component degrees and minutes are nonnegative whole counts, while the hemisphere supplies the sign. Zero is normalized to N/E so a negative-zero display is not mistaken for a different location.
DMS seconds are displayed to three decimal places with carry. A coordinate just below 13° can therefore display as 13° 0′ 0.000″, while the separate decimal output retains the original value to its own display precision. A formatted label does not add measurement accuracy.
At 90° latitude or 180° longitude, any additional positive minutes or seconds would exceed the supported range and are rejected. The tool does not silently wrap out-of-range longitudes or apply a hemisphere default from another program.
A few questions, answered
Does the converter use my device location?
No. It operates only on the values you enter and makes no geolocation or map request.
Why can the rounded DMS label differ slightly from the decimal value?
The two displays have different rounding precision. The DMS carry is a display operation, not a change to the stored decimal calculation.
Does changing DMS to decimal improve a survey?
No. Notation, measurement accuracy and coordinate reference transformations are separate issues.