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Discount Calculator

The sale price after one discount or several — which do not add up the way almost everyone expects.

Enter the price and one or more discounts.

Discounts, applied in order

Applies to the already-reduced price, not the original.

Coupon and sales tax

A flat amount off, taken after the percentages.

Charged on the discounted price, not the original.

Exact calculation. Given your inputs, this is the answer — no estimation involved.

How this calculator works

A single discount is simple: multiply the price by what is left after taking the percentage off. The interesting case is two or more.

"20% off, then an extra 10% at checkout" is not 30% off. The second discount applies to the already-reduced price, so $100 becomes $80 and then $72 — a total of 28%. The stack is always worth less than the sum of its parts.

The gap grows with the numbers, and at the top it becomes obvious: 50% then 50% is 75% off, not free. Stated plainly nobody would get that wrong, and in a basket with a coupon code people get it wrong constantly.

One genuinely useful consequence: because the discounts multiply, the order they are applied in cannot change the total. A cashier scanning coupons in a different sequence gets the same answer, every time.

Sales tax is different and comes last, charged on the reduced price. That is why a discount saves you slightly more than the sticker difference suggests.

The formula

Exactly what happens to your numbers, step by step.

  1. One discount

    final = price × (1 − discount)

  2. Several

    final = price × (1 − d₁) × (1 − d₂) × …

    Multiplied, never added. Order makes no difference to the result.

  3. The equivalent single discount

    effective = 1 − (1 − d₁)(1 − d₂)

A worked example

A $249.99 jacket at 25% off, with an extra 15% code, plus 8.25% sales tax.

What you enter

Original price
$249.99
Discount
25%
Then
15%
Sales tax
8.25%

Step by step

After 25%
$187.49
After a further 15%
$159.37
Adding the percentages suggests
40% off
The real total is
36.25% off
With tax
$172.52

$159.37 before tax — 36.25% off, not 40%

The gap here is under ten dollars, which is why the mistake survives: it is never large enough on one purchase to force anyone to check. It is simply always in the store’s favor.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

  • Discounts are applied one after another, each to the price the last one left.
  • A coupon amount comes off after the percentages.
  • Sales tax is charged on the discounted price.

What this cannot tell you

  • Some promotions do not stack at all, and stores decide the rules. "Cannot be combined with other offers" is common and this cannot know about it.
  • Buy-one-get-one and similar offers are a different calculation — a BOGO is effectively 50% off across two items only if you wanted both.
  • It does not know whether tax applies to the item. Groceries, prescriptions and clothing under a threshold are exempt in many states.
  • It cannot tell you whether the original price was ever real. A discount from an inflated list price is arithmetic on a number that was chosen to make the discount look good.

Questions people ask

How do I calculate a discount?

Multiply the price by the discount to get the saving, or by one minus the discount to get what you pay. 25% off $80 saves $20 and leaves $60.

Is 20% off then 10% off the same as 30% off?

No, it is 28% off. The second discount applies to the reduced price, not the original — $100 becomes $80, then $72. Stacked discounts are always worth less than the sum.

Does the order of discounts matter?

Not to the total. Because the discounts multiply, 20% then 10% gives exactly the same price as 10% then 20%. It genuinely does not matter which coupon is scanned first.

Is sales tax charged before or after the discount?

After, on the price you actually pay. That means a discount saves you a little more than the shelf difference, because you avoid the tax on the amount discounted too.

Further reading

Related calculators

Sources and review

This calculator uses standard arithmetic with no external rules or published rates, so there is nothing to cite beyond the formulas shown above.

Methodology version 1.0.0 · Last reviewed

Cite this calculator

For coursework, a resource list or your own site. How every calculator is built and checked is set out on the methodology page.

Citation

Chalk Calculator. (2026, September 20). Discount Calculator (Methodology version 1.0.0). https://chalkcalculator.com/discount-calculator/

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