Discount Calculator

How the discount calculator works

The calculator starts from the original price times quantity, applies the main discount, then any second stacked discount to the already-reduced amount, adds sales tax on the discounted subtotal, and finally adds shipping or fees. You see the final price and exactly how much you saved.

Formulas

Sale price = price × (1 − discount ÷ 100)

Stacked: final = price × (1 − d₁ ÷ 100) × (1 − d₂ ÷ 100)

Total = discounted subtotal + tax + shipping

Worked examples

• $120 with 20% off — 120 × 0.80 = $96, saving $24.
• $120 with 20% off + extra 10% off — 120 × 0.80 × 0.90 = $86.40. The combined discount is 28%, not 30%, because the second discount applies to the reduced price.
• Adding 8% tax — $86.40 × 1.08 = $93.31 at checkout.

Why stacked discounts never add up

Two coupons of 20% and 10% feel like 30% off, but they are not — the second is taken from the already-reduced price, so the real saving is 28%. The order does not change the final total (0.8 × 0.9 equals 0.9 × 0.8), but it always lands below the simple sum. The only case where percentages truly add is when both are calculated from the original price, which is rare in retail.

Percent-off vs. amount-off deals

Deals come in two forms: a percentage off ("20% off") or a fixed amount off ("$25 off"). Which wins depends on the price — $25 off beats 20% off on anything under $125, but 20% off pulls ahead above it. When you are choosing between coupons, convert both to a final price and compare; the calculator's saved-amount figure makes that comparison quick.

To add or strip tax on its own, use the VAT / sales tax calculator, or check the underlying math with the percentage calculator.