Maidenhead locator to latitude and longitude
Decodes a Maidenhead (QTH) locator of 2 to 10 characters, in any letter case, to the center and bounds of its cell.
Go the other way: Latitude and longitude to Maidenhead locator →
The locator's cell is centered at 40.4375°, -79.958333333°.
- Center longitude
- South edge
- West edge
- North edge
- East edge
Provenance
- Computed by
- geodesy.grid-ref.maidenhead-inverse 1.0.0, core 0.1.0
- Model
- IARU Maidenhead locator definition
- Accuracy
- Exact cell bounds
- Notes
- None
- Cites
- International Amateur Radio Union, Region 1, VHF Managers Handbook: the Maidenhead Locator System
Something look off?
How we got thisFormula, worked example, sources, and proof
Model: IARU Maidenhead locator definition
Accuracy: Exact cell bounds
When to use this: Use this when a locator arrives from a log, a spot, or a QSO and you want the position: it returns the center of the square and its bounds, in any letter case and at any length from two to ten characters. It is the counterpart of the encoder: a locator from a log, a cluster spot, or a QSL card becomes a position you can plot, measure a bearing to, or hand to a rotator.
Limitations: The locator names a square, so the station is somewhere inside it rather than at the center; a four-character locator is a degree of latitude by two of longitude. Treat the center as a representative point and not a surveyed position. Two-character and four-character locators cover very large areas, so a distance computed from them carries tens or hundreds of kilometers of uncertainty. The locator says nothing about the station's height or its antenna.
Worked example: FN00ak. Source: add-geodesy-suite scenario: the Pittsburgh subsquare.
You enter
- Locator
- FN00ak
You get
- Center latitude
- 40.4375°
- Center longitude
- -79.958333333°
- South edge
- 40.416666667°
- West edge
- -80°
- North edge
- 40.458333333°
- East edge
- -79.916666667°
Review: Not yet independently reviewed by a geodesist.
Last verified: 2026-09-19, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.
Status: version 1.0.0, core 0.1.0. See this tool in the verification report.
Changes
- 2026-09-19, changed: The GARS, GEOREF, Maidenhead, and USNG tools are stable, both directions. They reproduce NGA's GARS band definitions, the Wikipedia GEOREF (NAS Patuxent River) and Maidenhead (W1AW) examples, and the FGDC USNG Washington Monument, and match GeographicLib, pygeodesy, an exact Maidenhead reference, and NGA GEOTRANS on thousands of points. Results are unchanged apart from the fix below. Changelog
Checked against: 25 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.
Sources
- VHF Managers Handbook: the Maidenhead Locator System, International Amateur Radio Union, Region 1, IARU Region 1 VHF Managers Handbook, version 10.03. The QTH locator: fields, squares, subsquares, and extended squares.