Discount Calculator

A percent-off sign tells you the discount but not the price you will pay, and the arithmetic gets slippery when a second discount stacks on top. This calculator returns the final price, the dollars saved, the effective percentage off and the price after tax, so you can compare a sale against a competitor's offer at a glance.

The important rule is that stacked discounts multiply rather than add. Twenty percent off and then an extra ten percent off is not thirty percent — the second discount applies to the already-reduced price, so the total is 1 − (0.8 × 0.9) = 28% off. The gap grows with the size of the discounts: fifty percent off plus fifty percent off is 75% off, not free.

Order of operations matters for taxes too. Sales tax is charged on the price after all discounts, which is why the final figure can be lower than a quick mental estimate suggests. Some retailers advertise a discount and then add fees; entering the tax rate here shows the true amount out of pocket rather than the sticker price.

Use the effective percentage off field to compare offers that are expressed differently. A store offering 25% off is beating one offering 10% plus a 10% clearance reduction (which is 19%), and the difference is exactly the kind of thing that is easy to misjudge at a glance. Round the final price up mentally for budgeting, and the total here is a good guide to what the register will show.

How the math works

Price after the first discount = original × (1 − first discount ÷ 100).
Price after the second discount = that result × (1 − second discount ÷ 100).
Effective percent off = (1 − final price ÷ original) × 100, which is less than the sum of the two discounts.
Price with tax = the final discounted price × (1 + sales tax ÷ 100).

Frequently asked questions

How do I calculate a discount?

Multiply the price by one minus the discount rate as a decimal. Twenty-five percent off $120 is $120 × 0.75 = $90. The saving is the difference, $30.

Is 20% off plus 10% off the same as 30% off?

No. The second discount applies to the reduced price, so the combined discount is 28%, not 30%. Stacked discounts always multiply, and the gap widens as the discounts get larger.

What is the effective discount?

It is the single percentage that would produce the same final price. It is the honest way to compare a stacked offer against a flat one: 10% plus 10% is 19%, so a flat 20% off is the better deal.

Is tax charged before or after the discount?

After. Sales tax applies to the price you actually pay, so the discount reduces the tax as well. Entering your rate here shows the out-the-door amount rather than the pre-tax figure.

Does this work for coupons and clearance together?

Yes, if the store allows stacking. Enter the coupon as the first discount and the clearance reduction as the second. If the coupon says it cannot be combined, only one applies — enter the better one alone.

Why is the price with tax higher than the final price?

Because sales tax is added at checkout on top of the discounted price. The tax rate varies by state and city, so entering your local rate gives the most accurate out-of-pocket figure.

This calculator is an educational estimator. It is not financial, medical, tax, or legal advice, and it does not account for fees, local rules, or your personal circumstances. Confirm decisions with a qualified professional.

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How the math works

Frequently asked questions

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