Each 4-digit, 1 degree in latitude X 2 degrees in longitude, maidenhead grid division is divided into 24 X 24 = 576 6-digit subgrids. Each subgrid is 2.5 minutes in latitude X 5 minutes in longitude. Whereas the distances represented by these lat-lon divisions are fairly constant for the latitude dimension, the longitude distances vary with latitude. As an example, the southern edge of EL16 (26 deg N lat) is 124.4 miles (200.2 km) across, while the northern edge of EN18 (49 deg N lat) is 90.9 miles (146.3 km). This affects the diagonal distances, of course, as well. The table below shows the variation in grid and subgrid width as well as in the diagonal distances across each.

To download an exellent program to convert between lat-lon and maidenhead grids, and to calculate bearing (including reverse) and distance in miles or kilometers, go to the W4SM site; scroll down to and select "New Improved" WinGrid Ver4.1 (wingrid.exe).

Calculations are NOT +/- 1%, but they are close; the distances showing two digits after the decimal point should most likely be rounded off, e.g. call "5.18" 5.2, "5.14" 5.1, etc.