tool · maidenhead
Grid locator: your square on the map
The Maidenhead locator is the radio amateur postal code: GG66ri states, in six characters, where a station is located with an accuracy of about 5 km. This is what goes into the FT8 QSO and the QSL card. Enter a coordinate, choose a city or tap on the map.
Coordinate and locator
Both sides converse: adjust either one.
The position stays on your device.
Longitude and latitude become letters and numbers through successive divisions: a 20° by 10° field (A to R), a 2° by 1° square (0 to 9), a 5' by 2.5' subsquare (a to x), and a 30" by 15" extended square (0 to 9).
Between two locators
From the top square to any other.
Distance via the haversine formula over a 6,371 km sphere. Initial azimuth: atan2(sen Δλ · cos φ2, cos φ1 · sen φ2 - sen φ1 · cos φ2 · cos Δλ). The return path is not just adding 180°: it is the azimuth calculated from the other side. Long path: point to the opposite side and travel the remaining 40,030 km.
Map
Tap to mark the origin or destination.
Sources
The calculations run in your browser, nothing leaves here. Each formula was checked against the references below.
- IARU Region 1, VHF Managers Handbook: Maidenhead locator system. field, square, subsquare and extended square
- ARRL, "The Maidenhead Locator System" (Grid Squares)
- Haversine formula and initial azimuth: Ed Williams, Aviation Formulary. average Earth radius 6,371.0088 km (IUGG)
- Country outlines: Natural Earth (public domain)