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// myloanmath
Discount Calculator
Find the sale price from a discount, or the discount from a sale price — with correct math for stacked discounts.
Why stacked discounts don't just add up
"20% off, plus an extra 10% off" feels like it should mean 30% off total — but it doesn't, and the gap is bigger than people expect on larger purchases. The second discount applies to the price after the first discount already reduced it, not to the original price. On a $100 item: 20% off brings it to $80, then 10% off that $80 brings it to $72 — a combined discount of 28%, not 30%. The two percentages compound against a shrinking base rather than simply adding together.
This matters most when a store advertises "extra 20% off already-reduced items" — the true final price is always a bit higher than naively subtracting both percentages from the original price would suggest.
Frequently asked questions
Do two discounts add together?
No — this is a common mistake. 20% off, then an additional 10% off, is not 30% off total. The second discount applies to the already-discounted price, so the real combined discount is 28%, not 30%.
How do I find the discount percentage if I only know the original and sale price?
Use the reverse calculator below the main tool — enter both prices, and it calculates the exact discount percentage and amount saved for you.