Grid Square Tools
Convert between Maidenhead locators and coordinates, and measure distance and bearing between two grids — all in your browser. 网格坐标与经纬度互转，并计算两点间距离与方位角——全部在浏览器本地完成。
A. Locator to Coordinates网格转经纬度
B. Coordinates to Locator经纬度转网格
C. Distance and Bearing距离与方位角
The Maidenhead locator system divides the Earth into a grid that hams use everywhere coordinates would be clumsy: contest exchanges, satellite passes, microwave schedules, VUCC awards. This tool converts a 4- or 6-character locator to the latitude and longitude of its center, converts coordinates back to a 6-character locator, and computes the great-circle distance and initial bearing between two locators.
Reading a locator is easy once you see the pattern: the first pair of letters covers the world in 20° × 10° fields, the digits narrow it to 2° × 1° squares, and the final pair of letters divides each square into 24 × 24 subsquares of about 5 × 2.5 arc-minutes. So JO22db and JO22DB are the same place (case doesn’t matter), and the tool accepts either. Distances use the haversine formula on a spherical Earth — accurate to well under a percent, which is all contest scoring and beam headings need.
The default example is the classic transatlantic path: JO22 (Amsterdam area) to FN20 (New York area) is about 5,943 km at an initial bearing near 291° — west-northwest, not due west, because great-circle routes bend toward the pole. That bend surprises people the first time they aim a beam by the map instead of the math; trust the bearing, the map projection is what lies.
Everything runs locally in your browser — no lookup leaves the page. Pair this with the Antenna Calculator when planning a station, and the repeater tools when you need stations near a grid rather than the grid itself.
Not sure of your own locator? Check your station coordinates on any map app, drop them into converter B, and you have the 6-character square to put on your QSL card and QRZ page — most hams only ever need their own plus the other station’s.
Frequently asked questions
What is a Maidenhead grid locator?
It's the location system hams use worldwide for contests, awards (VUCC) and weak-signal work. A 4-character locator covers a 2° × 1° area; 6 characters narrow it to about 5 × 2.5 arc-minutes — roughly 6 × 4 km at mid-latitudes.
How big is a 6-character grid square?
At the equator a 6-character subsquare is about 5.6 km east-west and 4.6 km north-south; it shrinks east-west as you approach the poles. For antenna aiming and distance scoring, the square's center is accurate enough.
Does the converter lose precision?
Yes — both conversions use the center of the square. Converting a 4-char locator and back returns the same square; going from coordinates, you get the square that contains the point, not the point itself.
Which bearing do I use for my antenna?
Point your beam at the initial (forward) bearing given here — that's the short-path heading from your station. The long path is roughly the opposite direction (add or subtract 180°).