There is no simple formula to determine the number of forklifts required based on physical plant or warehouse size. There are too many other parameters that come into play, such as:

1. Number of unit or pallets loads to be received each day.
2. Number of units to be shipped each day
3. Is the facilitity a warehouse or a manufacturing facility.
4. What distance do loads need to be moved from point A to B to C, etc.
5. How high loads are to be stored , how many pallet locations are requireed.
6. Type of trucks to be used - electric or engine powered
6. Etc, Etc, Etc.

The number of units required is best determined by people in shipping, receiving, manufacturing, production, warehousing and of course budget.