Discount Calculator
Work out sale prices and savings from a percentage off, reverse a discount from a sale price, or stack two discounts to find the true effective discount — with optional tax.
Written by the CalcBundle Research & Editorial Team · Reviewed by the Quality Review Team · Transparent formulas · results are estimates, not advice. · Updated
Sale price
Enter an original price greater than zero.
What is a discount calculator?
A discount calculator turns an original price and a discount into a sale price and savings — and back again. It also handles the tricky case of stacked discounts, where the maths is not what most people expect.
How to calculate a discount
- Discount amount = Original price × discount %
- Sale price = Original price − discount amount
- Reverse: discount % = (original − sale) ÷ original × 100
Multiple (stacked) discounts
This is the part people get wrong. Two discounts multiply, they do not add. A 20% discount followed by an extra 10% is not 30% off:
- $100 − 20% = $80
- $80 − 10% = $72
- Effective discount = 28%, not 30%
Percentage off vs final price
The calculator shows both the amount saved and the effective percentage, so you can compare offers fairly. This matters for shoppers comparing “30% off” against “$25 off”, and it matters even more for sellers, because the headline discount and the real cost to your business are two different things. To make sure a promotion is still profitable, check it against your profit margin and set prices with the product pricing calculator.
The margin cost of a discount
A discount is the most immediate lever in retail, but it is also the most misunderstood, because every point of discount comes straight out of profit. If a product sells for $100 at a 40% margin, a 20% discount does not merely trim 20% from the top line — it takes $20 out of the $40 of profit, cutting earnings on that sale in half. That is why a seemingly modest promotion can quietly erode profitability, and why high-margin categories can afford far deeper discounts than thin-margin ones. Before advertising a sale, it is worth calculating how much extra volume it must generate simply to stand still.
Worked example
A $100 product at 20% off costs the shopper $80, a $20 saving. Stack another 10% on top and it falls to $72 — a true 28% discount, not the 30% the two figures seem to promise. For the seller, if that $100 item cost $60 to deliver, the original $40 of profit becomes just $12 after the stacked discount: the effective discount of 28% wiped out 70% of the profit. Seeing both sides of the same transaction is exactly what a discount calculator is for.
Frequently asked questions
How do you calculate a discount?
Discount amount = original price × discount %. Sale price = original price − discount. For a $100 item at 20% off, the discount is $20 and the sale price is $80.
How do multiple (stacked) discounts work?
Stacked discounts are multiplicative, not additive. 20% off then 10% off is not 30% off — it is $100 → $80 → $72, an effective discount of 28%.
How do I find the percentage off from a sale price?
Discount % = (original − sale) ÷ original × 100. From $100 down to $80, that is 20% off.
Should tax be applied before or after the discount?
It depends on the jurisdiction and retailer. This calculator supports both: applying tax after the discount (most common) or to the original price before the discount.
Can a discount ever make a sale unprofitable?
Yes, and more easily than most people expect, because a discount comes entirely out of your margin, not your revenue. A 20% discount on a product with a 40% margin does not cut your profit by 20% — it halves it, since the whole discount is subtracted from the profit portion. On thin-margin items, even a modest discount can push a sale into a loss once fees and shipping are counted, which is why it is worth checking any promotion against your margin before running it.
How much extra volume does a discount need to break even?
Enough to make up for the lower margin on every unit, which is often a surprisingly large amount. If a discount cuts your contribution margin by a third, you need to sell roughly 50% more units just to earn the same total profit. This is the hidden cost of discounting: it can boost sales figures while leaving profit flat or lower, so the volume uplift has to be real and substantial to justify it.
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Disclaimer. This calculator provides estimates for informational purposes only. Results are based on the information you enter and the assumptions used by the calculator. Actual financial, tax, business valuation, lending, marketplace or investment outcomes may differ. Consider consulting a qualified professional for decisions involving significant amounts of money. Results are estimates. Tax treatment of discounts varies by jurisdiction and retailer.