Can you direct me to an ink calculating formula for the amount of ink needed based on coverage and number of impressions?

Due to the differences in paper hold out and absorption, ink strength, and press conditions, no one ink estimating formula is particularly accurate. Any formula needs to be tweaked for the conditions at your location or even for different presses and papers; ink estimating still involves some witchcraft. Most ink manufactures can provide ink-estimating tables or have online calculators. The Printing Industries Press publication "Handbook of Graphic Arts Equations" contains ink-estimating formulas. The book includes a link to download PC/MAC software that has all the equations from the book in a desktop calculator. https://system.printing.org/index.php?dispatch=products2.view&product_id=1045