Discount Calculator

What Is a Discount Calculator?

A discount calculator works out the result of a percent-off deal. Enter the original price and the discount percentage to get the sale price and the savings. It also reverses the math: from a sale price and discount rate it recovers the original price, and from an original and sale price it finds the discount percentage.

Discounts appear on nearly every shopping trip — seasonal sales, clearance markdowns, and coupon codes all reduce what you pay. Running the numbers first shows whether a deal is genuinely good or only looks that way. This page covers the discount formula, all three calculator modes, worked examples, stacked discounts, common mistakes, and frequently asked questions.

Discount Formula

Two equivalent formulas give the sale price:

Fastest: for 20% off, multiply by 0.80 — a $90 item becomes $72.00.

How to Use This Discount Calculator

1. Select a mode. Choose Sale Price to apply a discount, Original Price to reverse a discount, or Discount % to find the percentage between two prices.
2. Enter your values. In Sale Price mode, type the original price and the discount percentage (25 for 25% off). In reverse modes, enter the sale price with the rate, or the original and sale prices.
3. Press Calculate. The tool shows the headline result — sale price, original price, or discount rate — plus the full breakdown of savings.

Worked Examples

Example 1: 20% Off a $90 Item

1. Savings = 90 x (20 / 100) = 90 x 0.20 = $18.00
2. Sale price = 90 - 18 = $72.00
3. One-step check: 90 x 0.80 = $72.00

Example 2: 30% Off a $49.99 Shirt

1. Savings = 49.99 x 0.30 = $15.00 (rounded from $14.997)
2. Sale price = 49.99 - 15.00 = $34.99

Example 3 (Reverse): An Item Costs $80 After a 20% Discount — What Was the Original Price?

1. Original price = 80 / (1 - 20/100) = 80 / 0.80 = $100.00
2. Check: 20% of $100 = $20.00; 100 - 20 = $80.00

Example 4 (Reverse): A $120 Item Marked Down to $90 — What Is the Discount Percentage?

1. Discount % = [(120 - 90) / 120] x 100 = (30 / 120) x 100 = 25%

Stacked Discounts: Why 20% + 15% Is Not 35% Off

Stores often let you combine a sale with a coupon, but the discounts apply sequentially — each one reduces the already-discounted price, not the original. You cannot add the percentages together. Example: a $200 item with 20% off, then an extra 15% coupon:

1. After the first discount: 200 x 0.80 = $160.00
2. After the coupon: 160 x 0.85 = $136.00
3. Effective discount = [(200 - 136) / 200] x 100 = 32%, not 35%

The general rule: multiply the keep-fractions. Effective keep = (1 - d1) x (1 - d2), so effective discount = 1 - (1 - d1) x (1 - d2). Two 50% discounts do not make an item free — they make it 75% off (0.50 x 0.50 = 0.25 kept).

Types of Discounts

• Promotional discounts: temporary sale prices and seasonal events — the most common type shoppers see.
• Coupon discounts: fixed-amount or percentage-off codes applied at checkout, often stackable with sale prices.
• Quantity discounts: lower unit prices when buying in bulk, common in wholesale and warehouse stores.
• Clearance markdowns: permanent price cuts to move out-of-season or discontinued inventory.

Common Discount Mistakes

• Adding stacked discounts. 20% + 15% = 32% effective, not 35%. Multiply the keep-fractions instead.
• Adding the percentage back to reverse a discount. A $80 sale price at 20% off came from $100, not $96. Divide by (1 - rate).
• Dividing by the wrong base for the discount rate. A $120 item marked down to $90 is 25% off (30/120), not 33% (30/90). Always divide by the original price.
• Trusting inflated list prices. A 70% discount means little if the "original" price was never actually charged. Compare against other retailers.
• Ignoring sales tax. Discounts apply before tax at most registers, so the final total is the discounted price plus tax.

Smart Shopping: Is the Deal Real?

A large percentage off an inflated list price can still be worse than a small discount on a fair price. Before buying, compare the sale price against two or three other retailers and check price-history trackers where available. Fake discounts — where the supposed original price is set far above the genuine market price — are common during big sale events. The calculator above tells you exactly what you pay and save; only you can judge whether the "original" price was real.

Quick Mental Math for Common Discounts

Calculating Discounts in a Spreadsheet

In Excel or Google Sheets, with the price in A1 and the discount % in B1: sale price = =A1*(1-B1/100), savings = =A1*B1/100.

Frequently Asked Questions

Related Calculators

These tools cover the percentage math that surrounds discounts:

• Percentage Calculator: all four percentage problem types, including percentage increase and decrease.
• Sales Tax Calculator: add tax to the discounted price for the true checkout total.
• Tip Calculator: work out gratuity and split the bill after your meal.
• Compound Interest Calculator: percentage growth applied repeatedly over time.
• Simple Interest Calculator: flat percentage rates applied once per period.
• Fraction Calculator: convert sale fractions to exact percentages.

Conclusion

Discount math is percentage-decrease math: Savings = Original x (Discount / 100), and Sale Price = Original x (1 - Discount / 100). Reverse it by dividing the sale price by (1 - rate), and find the rate between two prices with [(Original - Sale) / Original] x 100.

Stacked discounts multiply rather than add, reversing a discount means dividing, and the rate always divides by the original price. Use the calculator at the top of this page for instant results in all three modes.