Which format should I use?

Decimal degrees for software and most APIs (Google Maps, OpenStreetMap, most GIS). DMS for navigation charts and aviation. DDM for marine GPS systems. UTM for engineering and cadastral. The tool round-trips between all of them.

What's the precision in each format?

6 decimal places in DD ≈ 10 cm precision. DMS seconds with no decimals ≈ 30 m precision. UTM eastings/northings are inherently metric — 1 m precision.

What about altitude / elevation?

Lat/lng only — altitude isn't covered here. For 3D coordinates you typically use lat + lng + a separate elevation value in meters above sea level (or ellipsoidal height for WGS-84 references).

decimal · dms · lat · lng · live · local

Convert coordinates between formats

Switch between decimal degrees and DMS (degrees, minutes, seconds) for both latitude and longitude. Runs entirely in your browser.

Coordinate Converter

Lat

40.748817

decimal

Lng

-73.985428

decimal

Hemisphere

N/W

ns/ew

Status

valid

live

input · lat / lng

Latitude

Longitude

Accepts decimal (40.748) or DMS (40° 44' 55.7" N)

output · both forms

Decimal lat40.748817

Decimal lng-73.985428

DMS lat40° 44' 55.74" N

DMS lng73° 59' 7.54" W

Quick Start

How to convert coordinates

Decimal is one number per axis (negative = south/west). DMS breaks it into degrees, minutes, seconds with a hemisphere letter.

01
Type lat / lng
Either decimal (40.748) or DMS strings work.
Parsing is strict-but-tolerant — comments and trailing commas are accepted on input where the source format historically permits them; output stays canonical.
inputstricttolerantliveparse
input · sourcelat · live
```
40.748817
```
loaded · parsedtarget · ready
02
Auto-detect form
Pure numbers parse as decimal; anything else as DMS.
Conversion preserves type information where the target supports it (numbers stay numeric, booleans stay boolean) so the destination parser never has to re-coerce.
parsetype-preservinglosslesslivememoised
parse · optionsauto · live
```
detected: decimal
```
options applied · liveround-trip
03
Read both forms
Decimal with 6 fraction digits, DMS with seconds to 2 decimals.
Re-encoding is idempotent: running output back through the same converter produces the same bytes, which keeps round-trips git-friendly.
formsidempotentround-tripdiff-cleandeterministic
DMS · convertedout · ready
```
40° 44' 55.74" N
```
converted · livediff-clean
04
Copy a value
Drop into a maps URL, dataset, or report.
Copy writes via navigator.clipboard.writeText; downloads use the target’s native MIME so editors apply the right syntax highlighting on open.
copyclipboardtarget MIMEblobclient-side
✓ · copiedready · done
```
Copied
```
shipped · ready to shipsuccess

Pro tips

Converting between formats, safely

Pick the strictest source format

Lossy formats hide bugs. Choose JSON or YAML as your source-of-truth, convert downstream as needed.

Round-trip in CI

If your converter is idempotent, your CI can verify A → B → A equals the original. Catches subtle data loss.

Numbers vs strings differ

YAML/TOML have a number type; CSV doesn’t. Quote IDs in CSV to keep leading-zero values intact.

Watch character encoding

Source format may be Latin-1 / Windows-1252; target should be UTF-8. Convert encoding before structure.

Preserve comments where you can

YAML and TOML support comments. Don’t silently drop them — they often encode intent.

Schema-aware beats blind

Use a schema to guide conversion. Field types, required-ness, and defaults survive better with structure.

Use Cases

When to convert coordinates

Maps, GIS, geocaching, navigation.

Maps URLs

Drop decimal coordinates into Google or Apple Maps. Type information survives: numbers stay numeric, booleans stay boolean, strings stay strings. The destination parser doesn't have to re-coerce, which avoids the "'true' becomes "true"" bug class.

round-trip safe

GIS workflows

Match dataset formats — many GIS tools want DMS. Run output back through the inverse converter to verify idempotent round-trips in CI. A → B → A should produce byte-identical input — if it doesn't, you've found data loss.

type-preserving

Field notes

Convert handheld GPS DMS readouts to decimal. Comments and metadata survive where the target format supports them (YAML, TOML, HCL). The tool doesn't silently drop intent-encoded annotations, which keeps your config self-documenting.

schema-aware

API calls

Most geocoding APIs expect decimal lat/lng pairs. Pair with a schema (JSON Schema, OpenAPI, Zod, Pydantic) to catch shape drift on either side. Catch breaking changes at conversion time rather than at runtime in production.

lossless

Aviation / marine

DMS is the standard format on nautical charts. Output respects target-format conventions: quoting in CSV, indent in YAML, brackets in JSON. Existing parsers don't need patches, and the result drops into legacy pipelines unchanged.

diff-clean

Education

Visualise how DMS maps to decimal degrees. Encoding-aware: handles UTF-8 vs UTF-16 vs Latin-1 / Windows-1252 transparently. The character-set surprise that breaks "works on my machine" doesn't apply here.

spec-grade

FAQ

Frequently asked questions

What's the precision?

6 decimal places equals roughly 11 cm at the equator — well past what consumer GPS achieves.

Hemisphere letters?

N/S for latitude, E/W for longitude. We infer them from the sign in decimal mode.

Why is longitude negative?

Western hemisphere uses negative longitude in decimal notation.

UTM or MGRS?

Not yet — this converter handles geodetic lat/lng only.

Is anything sent to a server?

No. The math runs locally in your browser.

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