Grid Square Locator: Find Your Maidenhead Grid

How the Maidenhead locator works

The Maidenhead Locator System was adopted by the IARU Region 1 VHF working group at Maidenhead, England in 1980 and is now used worldwide for VHF/UHF contests, satellite and EME logs, FT8 messages and the ARRL VUCC award. Each pair of characters divides the previous box:

Longitude always comes first. Add 180° to longitude and 90° to latitude so both are positive, then divide.

Worked example: W1AW, Newington, CT

41.7147° N, 72.7272° W. Longitude −72.7272 + 180 = 107.2728°; latitude 41.7147 + 90 = 131.7147°.

• Field: 107.2728 ÷ 20 = 5 → F (6th letter); 131.7147 ÷ 10 = 13 → N.
• Square: remainder 7.2728 ÷ 2 = 3; remainder 1.7147 ÷ 1 = 1 → 31.
• Subsquare: remainder 1.2728° × 12 = 15 → p; remainder 0.7147° × 24 = 17 → r.

Result: FN31pr, the locator ARRL publishes for W1AW.

Distance and beam heading

The distance mode uses the haversine great-circle formula on a 6371 km sphere (within about 0.5% of the WGS-84 ellipsoid) and gives the short-path heading, the long-path heading and both distances. Headings are true north; add your local magnetic declination before turning a compass-aligned rotator.

Grid lines, rovers and VUCC

• VUCC counts 4-character squares. If you operate on a line or corner, you can give each square you are standing in.
• FT8 and most digital modes send only 4 characters; WSJT-X can send 6 in some messages.
• Your grid square is not a privacy-sensitive address: a square is roughly 170 × 111 km at 40° N. A 6-character subsquare is a few kilometers wide; an 8-character locator can identify a single street.

Grid locators are not in the FCC rules; Part 97 does not require them. For on-air rules see Can I transmit here? and the station ID builder.