International · Ham radio
Maidenhead locator converter.
Convert a 2, 4, 6 or 8 character Maidenhead grid locator to latitude and longitude, turn coordinates into a locator, and get the great-circle distance between two locators.
How it works: longitude is measured east from 180° W and latitude north from 90° S, then written as pairs (longitude character first): field A–R (20° × 10°), square 0–9 (2° × 1°), subsquare A–X (5′ × 2.5′), extended square 0–9 (30″ × 15″). Coordinates shown are the centre of the cell. FN31pr is 41.72917, −72.70833.
Locator to coordinates
Coordinates to locator
Distance between two locators
Result
Enter a locator, coordinates or two locators and press the button.
How Maidenhead locators work
The Maidenhead Locator System (also called the QTH locator or IARU locator) is a geocode used by amateur radio operators. It was adopted by the IARU VHF Working Group at a meeting in Maidenhead, England, in 1980, and in 1999 the IARU fixed WGS-84 as its datum. Characters come in pairs, longitude first and latitude second.
| Pair | Name | Characters | Cell size (lon × lat) |
|---|---|---|---|
| 1 | Field | A–R (base 18) | 20° × 10° |
| 2 | Square | 0–9 (base 10) | 2° × 1° |
| 3 | Subsquare | A–X (base 24) | 5′ × 2.5′ |
| 4 | Extended square | 0–9 (base 10) | 30″ × 15″ |
Worked example, FN31pr: F = 5 gives −180 + 5×20 = −80°, then 3 adds 6° for −74°, then p = 15 adds 15×(2/24) = 1.25° for −72.75°. Latitude: N = 13 gives −90 + 130 = 40°, 1 adds 1°, r = 17 adds 17/24 = 0.7083° for 41.7083°. The cell centre adds half a cell: 41.72917, −72.70833.
Distance: IARU Region 1 VHF distances are calculated between subsquare centres on a spherical Earth. This tool uses the haversine formula with a 6371 km radius between the centres of the two cells you enter, so a 4 character locator is measured from the middle of a 2° × 1° square and the result can differ from the true distance by tens of kilometres.
Case: the IARU shows subsquare letters in upper case, although lower case (as in FN31pr) is common in practice. This page accepts either and shows the upper-case form.
Not covered
Locators longer than 8 characters are not formally defined by the IARU and are rejected. A coordinate exactly on a cell border belongs to the cell to its north and east; +180° longitude wraps to −180°.
Sources
- Wikipedia, Maidenhead Locator System (structure, WGS-84, IARU Region 1 spherical distance rule; cites the IARU Region 1 2017 clarification)
- python maidenhead, to_location.py and to_maiden.py (reference implementation: mixed radix 18, 10, 24, 10; cell-centre output; used to check the test vectors)
- IARU Region 1, 24th General Conference report (2017) (clarification and extension of the IARU locator; upper-case letters)
Privacy and scope
This tool runs entirely in your browser. Nothing you type is transmitted, stored or logged. It only converts between locator notation and coordinates; it does not look up anyone’s station or confirm that a location is real.