How this profit calculator works
Enter cost price and selling price. The calculator finds Profit/Loss = Selling price − Cost price, then Percentage = (Profit/Loss ÷ Cost price) × 100 when cost price is greater than 0. Cost 100 and selling 120 give Profit/Loss 20.00 and Percentage 20.00%. Both figures use two decimal places.
A positive Profit/Loss is a gain. A negative value is a loss: cost 100 and selling 80 give −20.00 and −20.00%. Equal prices are break-even at 0.00 and 0.00%. Percentage is always relative to cost price on this page, so cost 80 and selling 100 is 25.00% because 20 ÷ 80 × 100 = 25.
Both amounts must be finite and at least 0. An empty field or a negative value leaves both lines as “--.” If cost price is 0, Profit/Loss is still the selling price, but Percentage is forced to 0.00% so the page does not divide by zero.
Tax, discount, or shipping are not modelled separately. Put the final cost and selling figures you want to compare into the two boxes. Check by hand: subtract cost from selling price, then divide that result by cost and multiply by 100.