Worked answers
What your result means
The sale price is what the item costs after the discount, and "you save" is the discount in dollars. The "you pay" percentage is the share of the original price left after the discount, which makes it easy to compare offers: 30% off and "pay 70%" are the same deal. Sales tax, if you add it, is charged on the discounted price. The other tabs answer the general percentage questions with the same maths: 15% of 80 is 12, 12 is 15% of 80, and 80 to 100 is a 25% increase, while 100 back to 80 is a 20% decrease because the starting value is the base.
How to use the Percent Off and Percentage Calculator
- Pick a tab: Percent off for a sale price, or a percentage question such as X is what % of Y or % change.
- For a discount, enter the original price and the percent off (for example 25 for 25% off).
- Optionally add your sales tax rate to see the total you will pay.
- Compare offers with the table, or share the result with Copy link.
Formula and worked example
savings = price × percent off ÷ 100sale price = price − savings = price × (1 − percent off ÷ 100)with tax = sale price × (1 + tax rate ÷ 100)P% of X = X × P ÷ 100X is what % of Y = X ÷ Y × 100X is P% of what = X × 100 ÷ Ppercentage change = (new − old) ÷ |old| × 100percentage difference = |a − b| ÷ ((a + b) ÷ 2) × 100
Worked example: 40% off $60. Savings = $60 × 0.40 = $24.00. Sale price = $60 − $24.00 = $36.00, which is 60% of the original price. The percentage tabs use the same maths: 15% of 80 is 12, 12 is 15% of 80, and 12 is 15% of 80. Going from 80 to 100 is a 25% increase, but 100 back to 80 is a 20% decrease, because the base changes; the percentage difference between 80 and 100 is 22.2222% either way round. Adding 15% to 80 gives 92, and taking 15% off gives 68.
Sale prices at common discounts
| Percent off | $20 item | $50 item | $100 item |
|---|---|---|---|
| 10% off | $18.00 | $45.00 | $90.00 |
| 15% off | $17.00 | $42.50 | $85.00 |
| 20% off | $16.00 | $40.00 | $80.00 |
| 25% off | $15.00 | $37.50 | $75.00 |
| 30% off | $14.00 | $35.00 | $70.00 |
| 40% off | $12.00 | $30.00 | $60.00 |
| 50% off | $10.00 | $25.00 | $50.00 |
| 60% off | $8.00 | $20.00 | $40.00 |
| 70% off | $6.00 | $15.00 | $30.00 |
Computed by the calculator above; sales tax not included.
Percentage change vs percentage difference
| From → to | Change | Change back | Difference |
|---|---|---|---|
| 80 → 100 | +25% | −20% | 22.2222% |
| 50 → 100 | +100% | −50% | 66.6667% |
| 100 → 150 | +50% | −33.3333% | 40% |
| 40 → 30 | −25% | +33.3333% | 28.5714% |
| 4 → 5 | +25% | −20% | 22.2222% |
| 200 → 50 | −75% | +300% | 120% |
Computed by the calculator above. A change and its reverse are different sizes; the difference is the same both ways. From 4% to 5% is a rise of 1 percentage point, which is a 25% increase.
Assumptions and limits
- Stacked discounts multiply rather than add: 20% off and then another 10% off is 28% off in total, not 30%.
- Sales tax is applied to the discounted price, which is how most US states handle store coupons and sales. Check your state for manufacturer coupons.
- Percentage change uses the starting value as its base (its size, if it is negative), so a change and its reverse differ: +25% then −20% returns to the start. This is the method in the US Bureau of Labor Statistics CPI FAQ.
- Percentage difference compares two values with no before and after. Its base is their average, so the order doesn’t matter. It is defined here for values of 0 or more.
- Percentage results show up to 4 decimal places (one third shows as 33.3333%); each step works from the unrounded numbers.
Frequently asked questions
How do you calculate the percentage off a price?
Multiply the original price by the percentage and divide by 100 to get the savings, then subtract the savings from the price. For 25% off $80: $80 × 25 ÷ 100 = $20 saved, so the sale price is $60.
What is 40% off $60?
40% off $60 is $36. The discount is $60 × 0.40 = $24, and $60 − $24 = $36, which is 60% of the original price.
Do two discounts add up?
No, they multiply. 20% off followed by another 10% off is 28% off in total, not 30%: you pay 80% of 90% of the price, which is 72%.
Is sales tax charged before or after the discount?
For store discounts and sales, US sales tax is generally charged on the discounted price, which is what this calculator does. Rules for manufacturer coupons vary by state.
How do I work out the discount percentage from two prices?
Subtract the sale price from the original price, divide by the original price and multiply by 100. An $80 item on sale for $60 is ($80 − $60) ÷ $80 × 100 = 25% off. Check it here: 25% off $80 gives a sale price of $60.
How do I find the percentage of two numbers?
Divide the part by the whole and multiply by 100. For 12 out of 80: 12 ÷ 80 = 0.15, and 0.15 × 100 = 15%. Exam marks work the same way: 425 out of 500 is 425 ÷ 500 × 100 = 85%. Use the X is what % of Y tab.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = 25% increase. From 100 to 80: (80 − 100) ÷ 100 × 100 = −20%, a 20% decrease. The two differ because the starting value is the base each time.
How do I find the original price from a sale price?
Divide the sale price by (1 − discount). If something costs $36 after 40% off, the original price was $36 ÷ 0.60 = $60.
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About this calculator
Written and maintained by Ahsan Khan. See how every number is calculated, and the test cases checked on every update, on the methodology page.
Sources
- Coupons Shouldn't Be Taxed, but Government Vouchers Should, Tax Foundation (Josh Barro, updated July 24, 2023) (accessed Oct 11, 2026)
- Grade 6: Ratios and Proportional Relationships (6.RP.A.3.c, percent of a quantity), Common Core State Standards Initiative (accessed Oct 22, 2026)
- Consumer Price Index Frequently Asked Questions: How do I read or interpret an index? (percent change), U.S. Bureau of Labor Statistics (accessed Oct 22, 2026)
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