The formula to calculate sale price, percent off, original price is given below. As per shopping discount formula, to find percent off, divide original value from sales price and subtract the obtained value from 1. Multiply the resultant with 100. To know sales price, subtract percent off from 1, divide it by 100 and multiply the obtained value with original price. To get the original price, subtract percent off from 1, divide by 100 and again divide the obtained value from the sale price.