Most inventory carrying-cost calculators give you a single percentage to plug into EOQ. That's fine if your business is "average". For everyone else, the breakdown matters: perishable inventory carries a much heavier obsolescence cost than a metal bracket. This tool computes each of the 5 standard components and sums them, so you know which cost is actually driving your holding cost.
Carrying cost (or holding cost) is the annual cost to keep one dollar of inventory on the shelf. APICS breaks it into 5 categories; some practitioners use 4 (combining storage and insurance), some use 6 (separating tax from capital). The 5-component version is the most common.
For perishables or fashion, shrinkage and obsolescence dominate. For industrial slow-movers, capital dominates. Know which before you optimize.
Plug the resulting annual % into the EOQ calculator as your H parameter (you'll need the per-unit number, not the %, so divide by your average per-unit cost). The breakdown tells you where the optimization is. If obsolescence dominates, your real problem is forecasting, not ordering. If storage dominates, your real problem is warehouse cost or slotting, not order size.