Apps · grid helper

Maidenhead grid helper

Find your grid square from the picnic table, look up a park’s listed grid from its POTA reference, catch a wrong-length grid before you upload, turn lat/lon into a locator and back, and get distance and beam heading between two grids. Free, no sign-in.

1 · Where am I

My grid

Your browser asks for permission first. Location is read only when you tap the button, and it stays on this device.

2 · Locator to map

Grid to lat/lon

3 · Coordinates to locator

Lat/lon to grid

Decimal degrees. Use a minus sign or N/S/E/W. You can paste “41.7147, -72.7272” into Latitude.

4 · Path

Distance and bearing

Great-circle path, center of one grid to center of the other. A grid is a box, not a point, so the real distance can be off by up to the uncertainty shown. That can be 100+ km with 4-character grids and a few km with 6. Bearings are true north, not magnetic.

5 · Park reference

Park to grid, and a log-grid check

Type a POTA reference to see the grid POTA lists for that park. Paste the grid from your log too, and this checks its length and whether it lands in the same square.

The listed point is often a park office, a trailhead, or the middle of the park, so it is a sanity check and not your picnic table. Use “Use my location” above for the grid you actually log. A valid grid has 4, 6 or 8 characters (FN10, FN10nc, FN10nc42). Five or seven usually means a typo. The lookup asks the public POTA park API through this site's existing park endpoint. Nothing else leaves your browser. Not affiliated with Parks on the Air®.

How locators work

Field, square, subsquare

A Maidenhead locator narrows a spot down in pairs. Two letters (A–R) pick a field, 20° of longitude by 10° of latitude. Two digits pick a square inside it, 2° by 1°, roughly 170 × 110 km in the mid-latitudes. Two letters (a–x) pick a subsquare, 5′ by 2.5′, about 7 × 4.6 km. Two more digits give the extended square, 30″ by 15″, well under a kilometre across.

Six characters is the usual choice for logging. It is what most loggers write to MY_GRIDSQUARE and GRIDSQUARE in ADIF, and it is fine enough to tell nearby parks apart. FT8 and many contest exchanges send four.

Checking a log? ADIF Doctor warns when QSOs have no MY_GRIDSQUARE and can stamp your grid onto them.

Free, no account. Everything except the park lookup is worked out in this browser and nothing is sent to a server. Typed values are remembered on this device only; your location is not saved. Independent tool, not affiliated with any award program.