Discount Calculator
Sales rarely come as a single tidy number. A 20% markdown may be followed by an extra 10% coupon, and sales tax is added at the till. This calculator applies the discounts in order, shows what you save and what you pay, and reveals the true combined discount, which is smaller than the two percentages added together.
How to use the discount calculator
- Enter the original price and the main discount.
- Add a second discount if you have a coupon, or leave it at 0.
- Enter your sales tax rate to see the total at the till.
Formula
Price after discounts = original × (1 − d₁) × (1 − d₂), then total = price × (1 + tax). Stacked discounts multiply: 20% then 10% off is 0.8 × 0.9 = 0.72, a 28% discount, not 30%.
Worked examples
Stacked discounts
A $200 item at 20% off, then 10% off: $200 → $160 → $144. You save $56, an effective 28% discount. With 8% tax the total is $155.52.
A single discount
$60 at 25% off is $60 × 0.75 = $45.
Smart shopping with percentages
Comparing offers
| Offer | On a $80 item | Price |
|---|---|---|
| 25% off | ×0.75 | $60.00 |
| 20% off + extra 10% | ×0.72 | $57.60 |
| $15 off | −15 | $65.00 |
| Buy one get one half off (two items) | 1.5 × price ÷ 2 | $60.00 each |
Beware headline percentages
“Up to 50% off” means only some items reach 50%. “Take an extra 20% off sale prices” stacks with the sale, but only on reduced items. Always calculate the final price rather than trusting the biggest number.
Reverse the maths
To find the original price, divide the sale price by (1 − discount). If a coat costs $84 after 30% off, the original price was 84 ÷ 0.7 = $120.
Tax and total cost
Sales tax usually applies to the price you actually pay. On a $144 sale price with 8% tax you pay $11.52 in tax and $155.52 in total. Check local rules, since tax treatment of coupons can differ.
Practice problems
Try these yourself first, then check your answer. The answers come from the calculator above.
- A $150 jacket is 30% off with an extra 10% coupon and 7% tax. What is the total?
Show answer
Sale price (before tax): $94.50
- A $60 pair of shoes is 25% off. What do you pay before tax?
Show answer
Sale price (before tax): $45.00
Common mistakes to avoid
- Adding percentages. Two consecutive discounts of 20% and 10% are 28%, not 30%.
- Applying tax before the discount when the tax is charged on the sale price.
- Comparing “% off” with “$ off” without converting to the same basis.
Frequently asked questions
How do I calculate a discount?
Multiply the price by the discount rate to get the amount off, then subtract it. Or multiply the price by (1 − rate) in one step.
How do two discounts combine?
They multiply. Apply the first, then apply the second to the reduced price.
Is sales tax charged before or after a discount?
In most places tax is calculated on the discounted price, but rules vary, so check your local practice.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount). If $68 is after 15% off, the original was 68 ÷ 0.85 = $80.
Reviewed September 26, 2026 by the SolveCalcPro editorial team. Found a mistake? Tell us; see our editorial policy.