How does the discount calculator work?
The calculator multiplies the price by the discount to find your savings, then subtracts that from the price. The formula is sale price = price × (1 − discount%), and your savings is price × discount%. A $80 item at 25% off saves you $20, for a sale price of $60. Add a sales-tax rate and it also shows the final total you pay.
Do stacked discounts add up?
No — stacked discounts multiply, they do not add. Taking 20% off and then an extra 10% off is 28% off, not 30%. The second discount applies to the already-reduced price: 1 − (1 − 0.20) × (1 − 0.10) = 0.28. The table below shows common combinations.
Is the discount taken before or after tax?
The discount comes first. Stores apply the discount to the item price, then charge sales tax on the lower, discounted amount. So a coupon also lowers the tax you pay. This calculator follows that order: discount first, then tax on the sale price.
How to calculate a discount by hand
- 1
Convert the discount to a decimal. Divide the discount percentage by 100. A 25% discount becomes 0.25.
- 2
Multiply the price by that decimal. That gives the amount you save. On an $80 item, $80 × 0.25 = $20.
- 3
Subtract the savings from the price. The result is the sale price. $80 − $20 = $60.
- 4
Add sales tax if it applies. Multiply the sale price by 1 plus the tax rate. At 8% tax, $60 × 1.08 = $64.80.
Discount reference tables
Quick references for what you pay, stacked discounts, and percentages as fractions.
What you pay by discount (per $100)
Sale price and savings on a $100 item — multiply by your price ÷ 100 for any amount.
| Discount | You pay | You save |
|---|---|---|
| 10% off | $90.00 | $10.00 |
| 15% off | $85.00 | $15.00 |
| 20% off | $80.00 | $20.00 |
| 25% off | $75.00 | $25.00 |
| 30% off | $70.00 | $30.00 |
| 33% off | $67.00 | $33.00 |
| 40% off | $60.00 | $40.00 |
| 50% off | $50.00 | $50.00 |
| 60% off | $40.00 | $60.00 |
| 70% off | $30.00 | $70.00 |
| 75% off | $25.00 | $75.00 |
Source: Socko calculation: price × (1 − discount%).
Stacked discounts: the real combined discount
An extra % off applies to the already-reduced price, so two discounts multiply rather than add.
| First discount | Then extra | Actual combined discount |
|---|---|---|
| 20% off | 10% off | 28.0% off |
| 25% off | 25% off | 43.8% off |
| 30% off | 20% off | 44.0% off |
| 40% off | 30% off | 58.0% off |
| 50% off | 20% off | 60.0% off |
| 50% off | 30% off | 65.0% off |
| 50% off | 50% off | 75.0% off |
Source: Socko calculation: 1 − (1 − a)(1 − b).
Common discounts as a fraction
Round discounts to a simple fraction to estimate the price in your head.
| Discount | Fraction off | Quick estimate |
|---|---|---|
| 10% off | 1/10 | Drop the last digit |
| 20% off | 1/5 | Divide by 5 |
| 25% off | 1/4 | Quarter off |
| 33% off | 1/3 | About a third off |
| 50% off | 1/2 | Half price |
| 75% off | 3/4 | A quarter of the price |
Source: Socko reference.
Frequently asked questions
How do I calculate a 20% discount?
Multiply the price by 0.20 for the savings, then subtract. A $50 item saves $10, so you pay $40. (Or just multiply by 0.80.)
What is the sale price after a 25% discount?
Multiply the price by 0.75. A $100 item is $75 after 25% off.
How do stacked or “extra % off” discounts work?
They multiply. 20% + an extra 10% is 28% off, not 30% — the second coupon comes off the already-reduced price.
How do I add sales tax to a discounted price?
Discount first, then multiply the sale price by 1 + tax. A $60 sale price at 8% tax is $64.80.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount). $60 after 25% off means the original was $80 ($60 ÷ 0.75).
Is 50% off the same as “buy one get one free”?
Only when you buy two of the same item — BOGO averages 50% off per item. For a single item, 50% off is the better deal.
Is the discount calculator free, and is my data saved?
Yes — it is free and runs entirely in your browser. Nothing you type is sent or stored.
This tool is for estimation and education, not financial advice. See our methodology for how these figures are calculated and sourced.