Discount Calculator

Calculate sale savings, stacked percentage discounts, and final prices.

Original Price

Discount Rate

Presets:

Add a second stacked discount (e.g. extra 10% off clearance)

How It Works

The Discount Calculator computes final markdown prices and net savings on sale merchandise.

It also handles stacked promotional discounts (such as an extra 10% coupon on clearance items already marked down 20%) by compounding successive price reductions rather than incorrectly adding percentages.

Formula & Calculation

Single Discount Formula

Final Price = Original Price × (1 − Rate)

Rate=Discount percentage divided by 100 (e.g. 25% = 0.25)

Savings=Original Price × Rate

Stacked (Double) Discount Formula

Effective Discount = 1 − ((1 − d₁) × (1 − d₂))

d₁=Initial discount decimal fraction (e.g., 20% = 0.20)

d₂=Secondary coupon decimal fraction (e.g., 10% = 0.10)

Retailers do not sum percentages directly (20% + 10% ≠ 30%). The secondary reduction applies only to the already-discounted subtotal.

Step-by-Step Example

Example: Stacked 20% + 10% Discount on $100 Item

Calculating the true final price and effective discount rate:

Step 1: Apply initial 20% markdown: $100.00 × (1 − 0.20) = $80.00→ $80.00 subtotal

Step 2: Apply secondary 10% coupon to remaining balance: $80.00 × (1 − 0.10) = $72.00→ $72.00 final price

Step 3: Determine total savings and effective rate: $100.00 − $72.00 = $28.00 savings→ 28.00% effective discount

The final price is $72.00. The effective combined discount is 28% (not 30%).

Assumptions & Edge Cases

Successive Discount Compounding: Stacked discounts are applied sequentially. 50% off followed by another 50% off leaves 25% of the original price (75% total discount), not free.
Tax Timing Order: In most retail jurisdictions, sales tax is assessed against the net discounted subtotal rather than the full manufacturer suggested retail price (MSRP).

Frequently Asked Questions

Why is 20% off plus 20% off not 40% off?

The second 20% discount is taken off the lower sale price, not the original sticker price. (1 − 0.20) × (1 − 0.20) = 0.64, which means you pay 64%, giving a 36% total discount.

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