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.

BOGO offers in percentage terms

The condition column is the whole story. A BOGO is only 50% off if the second item was something you would have bought anyway. If it was not, the discount on what you actually wanted is zero, and you have spent more than you planned.

In a spreadsheet

Enter 20% either as 0.2 in a plain cell or as 20% in a percentage-formatted one — never both, or the discount silently becomes 0.2%.

The percent off formula

Taking a percentage off is one multiplication. The step that trips people up is that the discount amount and the final price are two different numbers:

saving = price × percent ÷ 100 · final price = price × (1 − percent ÷ 100)

Going the other way — finding the discount percentage from two prices — divide the saving by the original price: an item cut from $80 to $60 saved $20, and 20 ÷ 80 = 25% off.

Percent off in Excel and Google Sheets

With the price in A2 and the discount rate in B2, formatted as a percentage:

Write 20% as 0.2 if the cell is formatted as a plain number, or as 20% if it is formatted as a percentage — not both, or the discount becomes 0.2%.

Discount and sales tax in the right order

Discount first, tax second. Sales tax and VAT apply to the amount actually charged, so a coupon reduces the taxable base as well as the price:

total = price × (1 − discount) × (1 + tax rate)

A $40 item at 25% off with 8% sales tax costs $30 × 1.08 = $32.40. Applying tax first gives the same answer here because multiplication commutes — but only when the discount is a true price reduction. Manufacturer coupons reimbursed to the retailer are often taxed on the pre-coupon price, which is why a receipt sometimes shows more tax than you expect.

UK and EU shelf prices already include VAT, so a "20% off" sign there reduces a gross price and no further tax is added at the till.

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