Minefields consist of an integer number of minefield units. From that, the minefield's radius is computed:

Minefield_radius =
   Sqrt(Mine_units)

Internally, PHost uses that exact value. In messages, the radius is reported as Trunc(Minefield_radius), the diameter is reported as 2 * Trunc(Minefield_radius).

Some clients evaluate the Mine_units directly to plot minefields a little more exact. For example, PCC plots Round(Minefield_radius).