I once had a patent (utility model 01242) for the calculator registered in Estonia, but I decided not to extend it: it has now expired.

Therefore I would like to give the math behind the calculator to the public domain:

In order to get the scales line up it is necessary to use a constant representing Euler ‘s Number “e” = . I used Excel spreadsheet in the following way:

- Column A: actual physical size of the calculator (disk) with small increments.
- Column B: target size in the scope (mRad) = EXP (0,235 * column A).
- Column C: actual targets size (cm) = 20 * EXP (0,235 * column A).
- Distance of the target (m) = Column B * 100.

This is how it would look like in Excel:

It takes some extra work to align the end result in the way you want for printing or production. The basic math however was fairly simple to get straight once a mathematician (much cleverer then I) suggested to use Euler’s constant.