Irish Calculators
Business

Discount and Reverse Price Calculator

Apply discounts or increases, work back from a paid price, or compare two price figures. Sequential discounts compound, while fixed coupons and retailer-specific conditions need separate treatment.

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Your numbers

%
One percentage per row, between 0 and 100. No headers.
Your figures stay on this device.

How the calculation works

Move between original and changed prices without confusing percentage bases. The operations cover discounts, increases, recovering an original price, sequential discounts and comparison of two known prices.

Discounted price = original × (1 − discount). Reverse original = paid / (1 − discount). Sequential price = original × product(1 − each discount). Increase price = original × (1 + increase).

  1. Identify the percentage base

    A normal discount or increase starts from original price. A reverse calculation starts from the reduced price and must recover the larger base.

  2. Perform the operation

    Discounts multiply by one minus the rate; increases multiply by one plus it. Reverse discounts divide by one minus the rate, and sequential discounts repeat the reduction.

  3. Compare the amounts

    Read original price, final price and saving together. Effective discount expresses the overall reduction relative to original price; increases appear as negative savings and discounts.

Worked example: Stacked discounts

Sample inputs demonstrate the method. They are not a forecast or product offer.

The example starts at €100. A 20% reduction leaves €80; the next 10% removes €8. The final €72 is €28 below the original price, making the effective discount 28%.

Price operation
Apply sequential discounts
Starting price (or paid price in reverse mode)
100
Sequential discount percentages
20 10

Expected result

Final price
€72.00
Effective discount
28%
Worked example: Reverse discount

Sample inputs demonstrate the method. They are not a forecast or product offer.

Price operation
Recover original price
Starting price (or paid price in reverse mode)
80
Discount or increase (%)
20

Expected result

Original price
€100.00
Saving (negative for increase)
€20.00

Understanding your result

Sequential discounts combine multiplicatively. Their order gives the same mathematical price here because the model contains percentages without retailer thresholds or intermediate rounding rules.

Prices must share a VAT basis. The calculator does not infer fixed vouchers, minimum spends or whether a promotion applies to a particular product.

Questions you might have

Do 20% off and another 10% off add up to 30%?

No. The second discount applies to the reduced price: €100 becomes €80 and then €72, a total discount of 28%.

Choosing the right inputs

Price operation
Choose the operation first. In reverse mode, the starting-price field means the amount paid after the discount rather than the original amount.
Sequential discount percentages
For sequential discounts, enter one percentage per row without headings. Each applies to the price remaining after the preceding reduction.
Discount or increase
Enter a rate such as 20 for 20%. Reverse discounts must be below 100%, because a free item does not reveal its original price.

Common mistakes to avoid

  • Do not add sequential discount percentages together.
  • Do not recover original price by increasing the paid price by the original discount percentage; that uses the wrong base.

Assumptions to check

  • Use amounts in one currency and one reporting period. Results are labelled EUR; the arithmetic also works for another consistent currency.
  • Use prices on the same VAT basis. Fixed-amount coupons, thresholds and rounding rules are not inferred.

Sources and method

Read our calculation and testing approach.