Percent Off Calculator

What this calculator does

This calculator handles the four common percent-off questions: (1) sale price from original + discount, (2) original from sale + discount, (3) effective discount when two promotions stack, and (4) after-tax total when sales tax applies to the discounted price.

Formula

Forward: savings = price × (percent ÷ 100) · sale price = price − savings

Reverse: original = sale ÷ (1 − percent ÷ 100)

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

After tax: total = sale × (1 + tax/100)

Variable definitions

• price / original — Original price before any discount.
• sale — Price after the discount is applied.
• percent / d₁ / d₂ — Discount percentages (e.g. 25 for 25% off).
• tax — Local sales tax rate as a percent.

Step-by-step calculation

1. Convert each discount percent to a decimal (divide by 100).
2. Multiply the original price by (1 − discount) for each discount you apply.
3. Subtract from the original to get the savings.
4. Optionally multiply by (1 + tax/100) for the out-the-door total.

Worked example

A jacket listed at $129.99 with a 30% off promo, plus an extra 10% off at checkout, with 8% sales tax.

• After first discount: 129.99 × 0.70 = $90.99
• After stacked discount: 90.99 × 0.90 = $81.89
• You save: 129.99 − 81.89 = $48.10 (~37% effective off)
• After 8% tax: 81.89 × 1.08 = $88.44

How to use this calculator

1. Pick Forward (price + discount) or Reverse (sale + discount).
2. Enter your numbers. Toggle Stacked to apply a second discount.
3. Enter a sales tax percent for the after-tax total.

Common mistakes

• Stacking percents by adding: 20% + 10% is not 30%. The actual effective discount is 28%.
• Forgetting tax: the pre-tax sale price isn't the out-the-door total — add your local tax rate.
• Tip vs discount confusion: "20% off" is a discount (subtract); "20% tip" is an addition.

Frequently asked questions