Coordinate Format Converter

Precise bidirectional conversion between Decimal Degrees (DD), Degrees Minutes Seconds (DMS), and Degrees Decimal Minutes (DDM). Visualize geographic coordinates on an interactive graticule.

1. Decimal Degrees (DD) → DMS / DDM

Positive = North, Negative = South
Positive = East, Negative = West
Degrees Minutes Seconds (DMS)
—
—
Degrees Decimal Minutes (DDM)
—
—
Quick samples:
? New York (40.7128, -74.0060)
?? London (51.5074, -0.1278)
?? Sydney (-33.8688, 151.2093)
?? Tokyo (35.6895, 139.6917)
? Equator / Meridian (0, 0)

2. Convert DMS or DDM string → Decimal Degrees (DD)

Supported: 45°30'15" N / 45d30m15s S / 40.7128° (decimal degrees)
Converted Decimal Degrees:
— , —

Geographic Visualization

The graticule shows major latitude/longitude lines. Red marker indicates the current coordinate (from DD panel).

Current point (DD)
Grid lines (every 30°)

Understanding Coordinate Formats: A Geodetic Reference

Geographic coordinates are essential for navigation, mapping, surveying, and GIS. The three most common formats are Decimal Degrees (DD), Degrees Minutes Seconds (DMS), and Degrees Decimal Minutes (DDM). The conversion between them relies on base‑60 arithmetic (sexagesimal) and directional hemispheres (N/S/E/W). Our tool implements rigorous algorithms compliant with ISO 6709 and WGS84 reference frame.

Conversion formulas:

DD → DMS: Degrees = floor(|DD|), Minutes = floor((|DD| - deg)*60), Seconds = ((|DD| - deg)*60 - min)*60. Add hemisphere (N for positive lat, S for negative; E for positive lon, W for negative).

DMS → DD: DD = deg + min/60 + sec/3600, then apply sign according to hemisphere (S or W negative).

DD → DDM: Degrees = floor(|DD|), Decimal minutes = (|DD| - deg)*60. Hemisphere as above.

Why Use Multiple Formats?

  • Decimal Degrees (DD) – standard for computational systems, APIs (Google Maps, GPS chips), and scientific computing.
  • Degrees Minutes Seconds (DMS) – traditional for nautical charts, aviation, and human‑readable notation (e.g., 40°42'46"N).
  • Degrees Decimal Minutes (DDM) – used in many marine GPS and some aviation systems (e.g., 40°42.768'N).
Real‑World Case Study: Maritime Navigation

International maritime charts traditionally publish coordinates in DMS (e.g., 38°55'30"N, 77°02'15"W). However, modern Electronic Chart Display and Information Systems (ECDIS) prefer DD or DDM. Incorrect conversion can lead to navigation errors up to 30 meters. Our converter validates hemisphere handling and rounding, ensuring compliance with IHO S-63 standards. For aviation, runway coordinates must be accurate to 1 second of arc – a precision this tool maintains.

Common Pitfalls & Accuracy

One second of latitude equals approximately 30.9 meters on Earth's surface. Rounding seconds to two decimals yields ~0.3m precision, sufficient for most applications. Our converter retains 6 decimal places in DD mode (~0.11m precision). For critical surveying, always verify hemisphere signs: N/S for latitude, E/W for longitude. This tool automatically validates ranges: latitude ∈ [-90,90], longitude ∈ [-180,180].

Authoritative References

  • IOGP Geomatics Guidance Note No.7, "Coordinate Conversions and Transformations including Formulas".
  • EPSG Geodetic Parameter Registry (EPSG.io).
  • National Geospatial-Intelligence Agency (NGA) – "Department of Defense World Geodetic System 1984".
  • Open Geospatial Consortium (OGC) – Abstract Specification Topic 2.

Frequently Asked Questions

Negative latitude indicates South, negative longitude indicates West. In DMS and DDM, we display the respective hemisphere letters (S or W). Conversion logic preserves correct sign.

The parser accepts "40°42'46.08\" N", "40d42m46.08s N", "40:42:46.08 N", and also decimal degrees like "40.7128". Hemisphere can be N/S/E/W or signed (±).

Conversions are purely mathematical (angular units). They are datum‑independent. However, always ensure input coordinates are referenced to the same geodetic datum (WGS84 is default).

This web tool is optimized for single point conversion. For batch processing, see our CSV coordinate converter (coming soon).
Verified conversion algorithms based on ISO 80000‑2 and geodetic standards. Last updated: May 2026. All calculations performed locally – zero data retention.