Discount Calculator
Calculate sale prices and savings instantly. Supports double discounts, tax after discount, and reverse price lookup — perfect for shopping season.
How to Calculate Discounts
Whether you're shopping Black Friday deals or comparing prices at the grocery store, knowing how to quickly calculate discounts helps you make smarter purchasing decisions. The math is simple once you know the formulas.
Basic Discount Formula
To find the sale price, multiply the original price by (1 minus the discount rate). To find just the savings amount, multiply the original price by the discount rate.
Sale Price = Original Price − Savings
Sale Price = Original Price × (1 − Discount % ÷ 100)
Savings = $120 × 0.30 = $36
Sale price = $120 − $36 = $84
Double (Stacked) Discounts
When a store offers "20% off plus an extra 10% off," many people assume this means 30% off. It doesn't. The second discount applies to the already-reduced price, not the original. This is called stacking or compounding discounts.
After 2nd discount: Price₂ = Price₁ × (1 − D₂ ÷ 100)
Effective total discount = 1 − (1 − D₁/100) × (1 − D₂/100)
After first: $100 × 0.80 = $80
After second: $80 × 0.90 = $72
Effective discount: 28% (not 30%)
Finding the Original Price
Sometimes you see a sale price and want to know what the original was. Divide the sale price by (1 minus the discount rate) to work backwards.
Original = $60 ÷ (1 − 0.25) = $60 ÷ 0.75 = $80
Tax After Discount
In most places, sales tax is calculated on the discounted price, meaning you save on tax too. This calculator applies tax after the discount, which is standard in the US and most other countries. The final price is: (discounted price) × (1 + tax rate).
Frequently Asked Questions
Multiply the original price by the discount percentage divided by 100. Subtract that from the original. Example: 25% off $80 → $80 × 0.25 = $20 saved → sale price $60.
You save $10. The sale price is $40. Calculation: $50 × 0.20 = $10, then $50 − $10 = $40.
They're applied sequentially. "20% off + extra 10% off" is NOT 30% off. The second discount applies to the already-reduced price. On $100: first = $80, then 10% off $80 = $72. Effective: 28%.
Divide the sale price by (1 − discount/100). If something costs $60 after 25% off: $60 ÷ 0.75 = $80 original price.
After. In most jurisdictions, sales tax applies to the discounted price. You save on tax too. This calculator applies tax after discount, which is standard.
Only if both items are the same price and you're buying exactly two. BOGO 50% off on a $40 item: you pay $40 + $20 = $60 for two, which is $30 each — effectively 25% off per item. But if items differ in price, the math changes.