Convert Calendar Days to Working Days (and Vice Versa) | 4 Day Work Week

Question

I have values corresponding to 'Calendar Days.' I'd like to convert this to 'Working Days.'

In this example, a 'Working Day' is defined by Monday through Thursday (4 days out of the possible 7 in a week).

Alternatively, I'd also like to convert 'Working Days' back to 'Calendar Days.'

The calculation will primarily be done and applied in Excel over many rows, so any MS Excel answers are appreciated.

Example:

Answer 1

This calculation can not be completed precisely from the data given.

In order to know exactly how many of the correct days there are in a period of that length, we would need to know the start day or end day.

However, we should get a reasonable approximation for large numbers like this by simply multiplying by our workday fraction. So n calendar days should be approximately n*4/7 working days.

This formula is pretty good for many purposes with large numbers, and will only be off by a few days at most.

However, it breaks completely for small numbers. For example, if our calendar days count was 3, the working days count could be 0, 1, 2, or 3 - and we do not have enough data to say which of those it actually is, given the current problem statement.

With similar caveats, the inverse operation should approximately go from working days to calendar days.

Also, real working days also often may be shifted around by holidays and the like.