Part of our Getting On The Air: Modes, Operations, and Making Contacts guide.
If you have used GridTracker, chased VHF contacts, or worked a satellite pass, you have run into grid squares already, that short alphanumeric code like DM43 or EM12ab that hams exchange as a compact stand-in for actual location. The system behind it, the Maidenhead Locator System, is simple once you see how it is built, and it explains why those codes show up constantly across so many different parts of the hobby.
How the grid is actually built
The Maidenhead system divides the entire globe into a grid, first into large fields identified by a letter pair, like DM or EM, each field roughly the size of a large US state, then subdivides each field further into 100 numbered squares, then into smaller lettered sub-squares within each of those. A four-character grid like DM43 gets you to roughly a 70 by 100 mile area, which is precise enough for most casual VHF or satellite work, while a full six-character grid like DM43an narrows that down to an area of just a couple of miles, useful for more precise contest scoring or distance measurement.
Why hams use this instead of just saying a city name
A grid square is compact, unambiguous, and works identically anywhere in the world regardless of language, unlike a city name which requires the other operator to actually know your local geography. It is also directly usable for calculation: software can instantly compute distance and bearing between two grid squares, which is exactly why award programs like VUCC track contacts by grid square rather than by city or county, and why contest software and satellite tracking apps lean on it so heavily.
Where grid squares actually get used
- VHF and UHF contesting, where working new grid squares, rather than new countries, is often the entire scoring objective.
- Satellite operating, where knowing your own and the other station’s grid square helps confirm and log a successful pass.
- Award chasing, most directly VUCC, the VHF/UHF Century Club award, which counts confirmed grid squares rather than countries.
- Digital mode software like GridTracker, which plots your FT8 and other digital contacts by grid square on a live map automatically.
Finding your own grid square
Numerous free calculators online will convert your street address or GPS coordinates directly into a Maidenhead grid square in seconds, and most logging software and digital mode apps display it automatically once you have entered your location during initial setup. Once you know your own grid square, working out a rough distance and bearing to another station’s grid, or plugging both into an online calculator for an exact figure, becomes a quick, routine part of chasing awards or planning a VHF contact.
Grid squares matter most in VHF/UHF Contesting, where they’re the primary scoring currency.