Maidenhead Locator Calculator

The Maidenhead Locator System is a geographic coordinate scheme adopted by the International Amateur Radio Union (IARU) at a meeting in Maidenhead, England in 1980. It encodes any point on Earth as a hierarchical alphanumeric string — typically 4, 6, or 8 characters — that is compact enough to exchange in a brief radio contact and precise enough to place a station within a few hundred metres. Every licensed amateur worldwide uses the same grid, making it a universal language for position reporting across HF, VHF, and satellite operation.

The 4-character grid square (also called a field-and-square locator) is the standard unit for most HF contacts and contest exchanges. It covers approximately 1° of latitude by 2° of longitude — roughly 111 km north-south and 222 km east-west at the equator, narrowing at higher latitudes as meridians converge. The first two uppercase letters identify a field (one of 324 globally), and the following two digits identify one of 100 squares within that field. For New York City, the 4-char locator is FN30.

Adding a 6th character pair — lowercase subsquare letters a through x — reduces the coverage area to about 2.5 minutes of latitude by 5 minutes of longitude, approximately 4.6 km × 9.3 km at mid-latitudes. This precision level is standard for VHF and UHF weak-signal work, POTA activation spotting, and FT8 decoding, where WSJT-X automatically exchanges 4-character grids during each QSO. The full 6-char locator for midtown Manhattan is FN30at.

An 8-character locator adds a final digit pair, cutting the area to roughly 15 arc-seconds of latitude by 30 arc-seconds of longitude — approximately 460 m × 580 m at 40° latitude. This level of precision is used in APRS beacons, microwave contest scoring, and some satellite tracking applications where station positions must be distinguished within a single city block. Knowing which precision level is required by each operating activity prevents reporting errors on contest logs and POTA submissions.

To find your grid square without a GPS, right-click on your location in Google Maps and select "What's here?" — the decimal coordinates appear at the bottom of the screen. Enter those directly into this calculator. Your logging software (WSJT-X, N1MM+, Ham Radio Deluxe) also accepts decimal coordinates and auto-populates the grid field. QRZ.com displays the 6-char grid on every callsign lookup page, which is convenient when searching for a DX station's location before a contest.

When activating POTA or SOTA from a boundary area, always verify which grid square your exact operating position falls in — the park boundary and the grid square boundary may cross within metres of each other, and logging the wrong grid invalidates the grid credit for chasers. Use the 6-char locator for POTA logs and the displayed SW-corner coordinates in this calculator to confirm you are inside the intended square before starting the activation.

For VHF contest purposes, the 4-char grid is almost always the unit used for multipliers, but know your 6-char locator for FT8 beacon work and for exchange with stations who are themselves near a grid boundary. A contact near the FN31/FN30 boundary, for example, lets both operators claim a grid-square bonus contact while simultaneously counting the QSO in the regular log.