Discount Calculator
See how much you save and what you pay after a percent-off discount.
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Enter the original price and the percentage off, and this calculator returns two numbers: the amount you save, and the price you actually pay. A $150 jacket at 20% off saves $30, leaving $120.
Both inputs are required — the price before any reduction, and the discount as a percentage rather than a currency amount. The savings figure is what comes off the price; the final price is what you hand over before any sales tax is added.
📖 Read the guide: How to Calculate a Discount (and Do Stacked Discounts Save More?)
Formula
Amount saved
savings = price × (percent off ÷ 100)
price is the pre-discount amount; percent off is the advertised reduction. Dividing by 100 converts the percentage to a decimal. Example: 20% off $150 → 150 × 0.20 = $30 saved.
Final price
final price = price − savings
Subtract the savings from the original price. Equivalently, price × (1 − percent ÷ 100). Example: $150 − $30 = $120 to pay.
Examples
| Example | Input | Result |
|---|---|---|
| 20% off | $150, 20% off | Save $30 · pay $120 |
| 30% off | $80, 30% off | Save $24 · pay $56 |
| Half price | $59.99, 50% off | Save $30 · pay $29.99 |
| Clearance | $45, 70% off | Save $31.50 · pay $13.50 |
| Small discount | $19.99, 5% off | Save $1 · pay $18.99 |
How to use the discount calculator
- 1Enter the original price.
- 2Enter the discount percentage (the “% off”).
- 3Read off the amount saved and the final price; copy or share the result.
How to calculate a discount
Multiply the price by the discount percentage (as a decimal) to get the savings, then subtract the savings from the price to get what you pay. A 25%-off item at $80 saves 80 × 0.25 = $20, so you pay $60.
To stack two discounts (for example 20% then an extra 10%), apply them one after another rather than adding them: 20% then 10% off $100 is $100 → $80 → $72, which is a 28% total discount, not 30%.
Sales tax and the final total
A discount is applied to the pre-tax price; sales tax or VAT is then added to the discounted amount. If you need the tax-inclusive total, calculate the discount here first, then use the VAT calculator on the discounted price.
Assumptions and limitations
- The discount applies to the pre-tax price. Sales tax or VAT is calculated on the discounted amount afterwards, so the figure here is not the checkout total in a jurisdiction that adds tax at the till.
- Two discounts do not add. 20% off followed by an extra 10% off $100 gives $72 — a 28% total reduction, not 30% — because the second discount applies to the already-reduced price. Run the calculator twice to stack them.
- Results are shown to two decimal places, or to as many places as you entered in the price if that is more — enter 3.499 and the answers come back to three places. The calculation itself is exact: the numbers you type are used as written rather than converted to binary floating point first, so a value like 1.005 is not quietly treated as 1.00499999.
- The savings figure is rounded once, with a half rounding up, and the final price is then calculated as price minus that rounded saving. This keeps the displayed figures adding back to exactly the price you entered. It does mean a half-price item can look uneven: 50% off 59.99 shows 30.00 saved and 29.99 to pay, because the true half, 29.995, cannot be shown in two places.
- Trailing zeros count as precision. Entering 59.99 gives answers to two places, while 59.990 gives answers to three — the second is read as a request to work to three places.
- The discount must be between 0% and 100%, and the price cannot be negative. A negative price has no meaningful 'what you pay' answer, and a discount above 100% would imply being paid to take the item; both return a message rather than a number.
- This calculates a straightforward percentage off one item. It does not handle buy-one-get-one offers, spend thresholds, member pricing, or discounts applied to a basket subtotal.
How this calculation is tested
The math for this tool lives in lib/calc-engine/money.ts — a plain function with no interface code around it. The page you are using and the automated tests call that same function, so the tests check the behaviour you actually get.
The tests check:
- a standard discount (20% off $150 = $30 saved, $120 to pay)
- a 0% discount leaving the price unchanged
- a pinned golden value (20% off $80 = $64.00, $16 saved) that fails the build if the formula ever changes
This calculation is also pinned by a golden-value regression test, which runs on every change and weekly in CI.
Automated tests reduce implementation errors — they confirm the code computes the formula it is supposed to. They are not a professional review, and they cannot tell you whether this formula is the right one for your situation. More detail on how calculations are built and tested.
Frequently asked questions
How do I calculate a percentage discount?
Multiply the price by the percent off (as a decimal) to find the savings, then subtract from the price. 25% off $80 saves $20, so you pay $60.
How do I stack two discounts?
Apply them in sequence, not by adding. 20% then 10% off $100 gives $72 (a 28% total discount), because the second discount applies to the already-reduced price.
Does the discount include sales tax?
No. Discounts apply to the pre-tax price. Add sales tax or VAT to the discounted total afterward.
Is my data saved?
No — calculations run entirely in your browser.
Embed this calculator
Add the Discount Calculator to your own website — free. Copy and paste this snippet:
<iframe src="https://numvella.com/embed/discount-calculator" width="100%" height="460" style="border:1px solid #e2e8f0;border-radius:12px" title="Discount Calculator — Numvella" loading="lazy"></iframe>Related calculators
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