How to Calculate a Discount: Percentage Off, Final Price, and Sale Math

Whether you're shopping in a sale or pricing products, discount calculations are essential daily math. Here are all the formulas you need.

Percentage Off Formula

Discount Amount = Original Price × (Discount % / 100)
Final Price = Original Price - Discount Amount

Example: $80 item at 25% off

Discount = $80 × 0.25 = $20
Final Price = $80 - $20 = $60

Final Price = Original Price × (1 - Discount%/100)

Example: $80 at 25% off:

$80 × (1 - 0.25) = $80 × 0.75 = $60

If you know original and sale price:

Discount % = ((Original - Sale) / Original) × 100

Example: Regular price $120, sale price $90:

((120 - 90) / 120) × 100 = (30/120) × 100 = 25%

Two discounts don't simply add — they compound.

Example: 20% off, then an additional 10% off:

First discount: $100 × 0.80 = $80
Second discount: $80 × 0.90 = $72

Total saved: $28 (not $30). Equivalent to a single discount of 28%.

Formula: Combined discount = 1 - (1 - d1)(1 - d2)

If you know the sale price and discount:

Original = Sale Price / (1 - Discount%/100)

Example: Item costs $63 after 30% off:

$63 / 0.70 = $90 original price

Always apply discount before tax:

1. Apply discount: $100 × 0.75 = $75
2. Apply tax: $75 × 1.08 = $81 (with 8% tax)

Never apply tax first, then discount — you'll calculate incorrectly.

A 50% markup is NOT the same as a 50% discount:

Markup is calculated on cost; discount is calculated on selling price.

Use our Discount Calculator to instantly calculate any sale price, discount amount, or original price.