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Conversion

DMS ↔ Decimal Degrees Converter

Enter degrees, minutes and seconds and the tool returns the matching decimal degrees, or paste a decimal value and the tool decomposes it back into D° M′ S″. North / East are positive; South / West are negative. Useful for GPS, mapping, surveying, marine navigation and astronomy.

Degrees ° / Minutes ′ / Seconds ″

Decimal degrees

Ranges: longitude −180 ° to +180 °, latitude −90 ° to +90 °. South / West are negative; North / East are positive.

Following ISO 6709: 1 ° = 60 ′ = 3600 ″, where one arcsecond ≈ 30.9 m at the equator. Useful for maps, GPS, marine and astronomy.

Formula

decimal = sign × (D + M ⁄ 60 + S ⁄ 3600) D = ⌊|decimal|⌋ M = ⌊(|decimal| − D) × 60⌋ S = (|decimal| − D − M ⁄ 60) × 3600

Frequently asked

Why does anyone still use DMS instead of decimal degrees?

History plus paper-map ergonomics. DMS comes from the Babylonian sexagesimal system (the same one used for hours / minutes / seconds), and nearly 4000 years of marine navigation and astronomy have stayed with it — international nautical charts, sky atlases and military MGRS still use DMS. To the human eye DMS reads more cleanly: 22°16′21″ is easier to plot on a printed grid, measure with a protractor and re-write than 22.27249°, and one arcminute conveniently matches 1.855 km on the ground for quick mental estimates. The computer era standardised on decimal internally (no wrap-around bugs, fewer scale issues), but human interfaces still surface DMS — Google Maps, Maps Maker, every Wikipedia infobox shows both.

How precise is one arcsecond? What ground distance does "22°16′21″" map to?

Latitude is fixed: the earth's equatorial circumference is ~40075 km, so 360 ° spans that distance → 1° ≈ 111.32 km, 1′ ≈ 1.855 km, 1″ ≈ 30.92 m. A whole-arcsecond reading therefore carries up to ± 15.5 m of inherent uncertainty — about the size of a small apartment block or a school playground. Longitude is only 30.92 m / ″ at the equator; it shrinks by cos(latitude) toward the poles. Hong Kong (lat ≈ 22.3°): 1″ ≈ 30.92 × cos(22.3°) ≈ 28.62 m. London (51.5°): ≈ 19.24 m. Near the polar circles it drops to a few metres. To reach building-level precision use one or two decimal arcseconds (21.34″ ≈ ± 0.15 m) or seven-plus decimals in DD (0.0000001° ≈ 1 cm). Civilian GPS C/A code is ~3–5 m, which corresponds to ~0.1″ or roughly five decimals in DD.

How do DMS, DM and DD differ — which should I use as input?

DMS (Degrees-Minutes-Seconds): 22°16′21.6″ — integer degrees, integer minutes, decimal seconds. Classic nautical and topographic maps, military reports. DM (Degrees-decimal-Minutes): 22°16.360′ — integer degrees, decimal minutes. The default output of most GPS receivers (Garmin, Magellan) because it is more precise than whole-second DMS while needing only two fields. DD (Decimal Degrees): 22.27267° — pure decimal. Used by computers, APIs, Google Maps URLs and the geometry stored in GIS shapefiles. Easiest to script and to parse. Rule of thumb: DMS for printed maps; DD for machines; DM for active field GPS work. This tool converts DMS ↔ DD directly. For DM, enter the decimal minutes in the minutes field and leave seconds at 0 (16.36′ → 16′ 21.6″, equivalent values).

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