Maidenhead Grid Locator
Convert between Maidenhead grid locators (used by amateur radio operators) and latitude/longitude coordinates.
e.g., JO31ok or IO91wm
Coordinates (Center)
Latitude
51.437500°
Longitude
7.208333°
Precision: Subsquare (~5km)
Grid Locator Structure
JO31ok73
JO
Field (AA-RR)
31
Square (00-99)
ok
Subsquare (aa-xx)
73
Extended (00-99)
Example Locations
London, UKIO91wm
New York, USAFN30
Tokyo, JapanPM95
Sydney, AustraliaQF56
What is the Maidenhead Locator System?
The Maidenhead Locator System (also called QTH Locator or Grid Square) is a geographic coordinate system used by amateur radio operators to quickly describe their location.
Grid Structure
- Field: 2 letters (A-R), covers 20° × 10°
- Square: 2 digits (0-9), covers 2° × 1°
- Subsquare: 2 letters (a-x), covers 5' × 2.5'
- Extended: 2 digits (0-9), covers 30" × 15"
Why Maidenhead?
Radio operators use grid squares because they're:
- Easy to communicate over voice or Morse code
- Shorter than full coordinates
- Sufficient precision for most radio contacts
- Used in contests and awards programs
Maidenhead in Geocaching
Grid locators appear in puzzles involving:
- Amateur radio (ham) themes
- Communication or technology puzzles
- Multi-format coordinate challenges
- International or travel-themed caches