Discount Calculator
Calculate sale prices after percentage discounts.
A discount calculator - or discount value calculator - finds the sale price of an item after a percentage discount is applied, along with the total dollar amount saved. This shopping savings calculator also handles stacked (double) discounts, which do not simply add together the way many shoppers assume.
Enter the original price and discount percentage to see how discount is calculated and find the sale price and savings amount.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| $50 item, single 20% discount | $40.00 sale price, $10.00 saved | Sale price = $50 × (1 − 0.20) = $50 × 0.80 = $40.00. Savings = $50 − $40 = $10.00. |
| $100 item, stacked 20% then additional 10% off | $72.00 sale price (28% effective discount) | First discount: $100 × 0.80 = $80. Second discount applies to $80, not $100: $80 × 0.90 = $72. Combined effective discount = 28%, not a flat 30%. |
The Discount Formula
The sale price equals the original price multiplied by (1 minus the discount rate as a decimal). A $50 item with a 20% discount becomes $50 x (1 - 0.20) = $40, a savings of $10. The same formula works for any single percentage discount, regardless of the item's price. The percent-off convention became standard retail practice in the 20th century because it lets a single advertised rate, like 25% off, apply uniformly across an entire range of differently priced items in a sale, without needing to calculate and post a unique dollar discount for every product.
Why Stacked Discounts Do Not Simply Add Together
A common shopping misconception is that two discounts - say, 20% off plus an additional 10% off - combine into a flat 30% off. They do not: the second discount applies to the already-discounted price, not the original price, so 20% off followed by 10% off produces a combined discount of 28%, not 30%. On a $100 item: 20% off brings it to $80, then 10% off that $80 brings it to $72 - a $28 total discount, slightly less than a flat 30% off would produce ($70).
Comparing Discount Offers That Are Framed Differently
Retailers sometimes frame equivalent-sounding offers differently - "$20 off $100" versus "20% off" are identical in this specific case, but percentage-based discounts scale with price while flat-dollar discounts do not, so comparing which offer is actually better requires converting both into the same format before judging which saves more money.
How to Use the Discount Calculator
- Open the Discount Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the discount calculator works.
Frequently Asked Questions
How do I calculate the sale price after a discount?
Multiply the original price by (1 minus the discount percentage as a decimal). For example, a $50 item at 20% off is $50 x 0.80 = $40.
Do two discounts stack by simply adding the percentages?
No. A second discount applies to the already-discounted price, not the original price, so 20% off plus 10% off equals a combined 28% discount, not a flat 30% off.
How much will I save with a specific percentage off?
Multiply the original price by the discount percentage (as a decimal) to find the dollar amount saved - a $50 item at 20% off saves $10 (50 x 0.20).
How do I calculate the original price from a sale price and discount percentage?
Divide the sale price by (1 minus the discount rate as a decimal). For example, a $40 sale price after a 20% discount means the original price was $40 / 0.80 = $50.
Is "$20 off $100" the same as "20% off"?
In this specific example, yes, since $20 is exactly 20% of $100 - but percentage discounts scale with price while flat-dollar discounts do not, so the two framings only match at that specific price point.
How do I compare two different-looking discount offers?
Convert both offers into the same format - either calculate both as a final price, or both as an effective percentage off the original price - before comparing which one actually saves more money.
Related Calculators
Percentage Calculator
Calculate percentages, percent of a number, and percentage changes fast.
Sales Tax Calculator
Calculate state and local sales tax totals.
Tip Calculator
Split restaurant bills and compute tip percentages per person easily.
Loan Calculator
Calculate monthly loan payments, interest charges, and loan payoff terms.
Mortgage Calculator
Estimate home mortgage payments including principal, interest, taxes, and insurance.
Compound Interest Calculator
Project future investment growth with daily, monthly, or annual compounding.
Last updated: September 29, 2026.