To do these calculations yourself, first must have your shipping cost matrix provided to you by your supplier/freight company.
The formula to calculate the shipping cost per centimeter squared based on a defined cost per measurement is as follows.
COST PRICE / (WIDTH CM x HEIGHT CM)
For the current size range, you are editing the price formula; you should match the range limit value with the step in your shipping cost matrix and retrieve the cost price value.
E.g. You have set a max size range that was 75cm, and in the shipping cost matrix, you have found the cost price for 75cm by 75cm to be a value of $98.00
Dimensions:75cm by 75cm
Price:$98.00
Calculation:98 / (75*75) = $0.017 per centimeter~ number was rounded to 3 decimals