What this calculator does
A single discount is easy arithmetic. Two stacked discounts are where retail maths gets counterintuitive: 30% off followed by a further 20% at the checkout is not 50% off. It is 44%, because the second discount applies to the already-reduced price.
This calculator handles both cases and reports the effective discount: the single percentage that would produce the same final price. That is the number worth comparing between offers.
The formula
Each discount multiplies the price by one minus its rate. Applying two in sequence multiplies both factors together, which always gives a smaller total reduction than adding the percentages would suggest.
| Term | Meaning |
|---|---|
| Sale price | What you actually pay after all discounts. |
| Saving | Original price less the sale price. |
| Effective discount | The single percentage equivalent to all discounts combined. |
The inputs explained
| Field | What to enter |
|---|---|
| Original price ($) | The price before any discount. |
| Discount (%) | The advertised discount percentage. |
| Extra discount at checkout (%) | A second discount applied to the already-reduced price. Leave at zero if there is only one. |
When to use it
Checking a stacked offer
Enter both discounts and read the effective figure. “Extra 20% off already-reduced prices” is worth less than it sounds, and the effective discount is what to compare against a competitor’s single offer.
Comparing two sales
A 40% discount on a $200 item beats a 50% discount on a $260 item. Running both takes a few seconds and settles it.
Working out a margin-safe discount
For sellers: the sale price needs to stay above cost. Increase the discount until the sale price approaches your unit cost, then check the remaining margin with the margin and markup calculator.
Reverse-checking a claimed discount
If a retailer claims 60% off but the price does not look right, enter the original and adjust the discount until the sale price matches. The gap tells you what the discount actually is.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Sale price on a $199 item
A single discount applied to a $199 item.
| Discount | You pay | You save | Effective discount |
|---|---|---|---|
| 10% | $179.10 | $19.90 | 10.00% |
| 20% | $159.20 | $39.80 | 20.0% |
| 25% | $149.25 | $49.75 | 25.0% |
| 30% | $139.30 | $59.70 | 30.0% |
| 40% | $119.40 | $79.60 | 40.0% |
| 50% | $99.50 | $99.50 | 50.0% |
| 70% | $59.70 | $139.30 | 70.0% |
What stacking a second discount really gives you
A 30% discount already applied, with a further checkout discount stacked on top.
| Extra discount | You pay | You save | Effective discount |
|---|---|---|---|
| 0% | $139.30 | $59.70 | 30.0% |
| 10% | $125.37 | $73.63 | 37.0% |
| 15% | $118.40 | $80.60 | 40.5% |
| 20% | $111.44 | $87.56 | 44.0% |
| 25% | $104.48 | $94.53 | 47.5% |
| 30% | $97.51 | $101.49 | 51.0% |
Questions
Why isn’t 30% off plus 20% off equal to 50% off?
Because the second discount applies to the reduced price, not the original. 30% off leaves 70%, and 20% off that leaves 80% of 70%, which is 56% of the original: a 44% total discount.
Does this include sales tax?
No. Enter the pre-tax price for a pre-tax result, or use the sales tax calculator to add tax to the discounted figure afterwards.
How do I work out the original price from a sale price?
Divide the sale price by one minus the discount rate. A $70 item at 30% off had an original price of $70 ÷ 0.7, which is $100.
What is a good mental method for percentages off?
Find 10% by moving the decimal point, then build from there. 30% is three times that; 25% is a quarter, so halve it twice.
To add tax to the discounted price, use the sales tax calculator. To compare value between pack sizes, see unit price comparison.