(Note: if you just need to calculate gross margin or mark up, please scroll down.) If you want to increase gross margin with a price increase, you should know how gross profit is calculated and assuming a drop in unit sales, how many unit sales are needed to maintain the same gross profit. On the other hand if you’re considering a sale you should know how many additional unit sales are needed to maintain the same gross profit. You need to know how total unit sales can drop (for a price increase) or need to increase (for a price...