Discount Calculator — Percent Off & Stacked Deals

What this Discount Calculator does

This English-language discount calculator handles the math that trips up most shoppers and deal-hunters: stacked discounts. When a store advertises "20% off, plus an extra 10%", many people add those figures and expect 30% off — but the actual effective discount is closer to 28%. The two percentages multiply against successive prices, not the original tag. This tool computes that correctly every time, then layers in sales tax (applied to the discounted price, not the original) and scales across any quantity you enter. The result screen shows the final per-item price, the total amount saved, and the true effective discount percentage so you can compare two competing offers side by side. Everything runs 100% client-side — your data never leaves your browser. No uploads, no tracking, no server logs. You can also use our [percentage calculator](/en/percentage-calculator/) when you need to work backward from savings to a rate.

Features

Percentage or fixed-amount discount. Enter a discount as a percent off (e.g. 25%) or as a flat dollar amount off the list price — whichever the coupon or promotion specifies.
Stacked second discount. Add a second discount that applies after the first — the tool multiplies them correctly instead of adding, so the effective overall discount is always accurate.
Sales tax on the discounted price. Tax is computed on the post-discount price, matching how retailers actually calculate it. Enter your local rate and the final total updates instantly.
Multi-quantity purchase total. Buying several items? Enter a quantity and the calculator returns both the per-item price and the full order total, useful for budgeting before the cart shows it.
Effective discount rate display. See the real combined discount percentage in one number — critical when comparing "30% off" against "20% + 15% off" to know which deal actually wins.
Discount value and savings breakdown. The result panel shows how much money you save (the discount value) separately from the final price, so you can judge whether an offer is worth it at a glance.

How to use the Discount Calculator

Fill in the fields from top to bottom and hit Calculate — results appear immediately below the form.

Enter the original price. Type the full list price before any discount, for example 149.99.
Set your primary discount. Choose percent or fixed amount, then enter the value — 20 for 20% off, or 30 for a $30-off coupon.
Add a stacked discount (optional). If the promotion stacks a second deal (like an extra 10% for loyalty members), enter it in the second discount field. The tool applies it to the already-reduced price.
Enter tax rate and quantity. Type your sales tax percentage and how many units you're buying. Leave quantity at 1 for a single item.
Read the results. The panel shows the discounted price per item, total tax, order total, amount saved, and effective discount percentage all at once.

Common use cases

Verifying the register price on a sale item. Punch in the shelf price and the advertised percent off before checkout. If the register rings a different number, you have the math ready to dispute it.
Comparing two competing promotions. "30% off" versus "20% off + extra 15%" — enter both scenarios and compare the effective discount percentage the tool reports. The stacked deal often wins by a small margin.
Budgeting a bulk or office supply order. Enter unit price, a volume discount, applicable tax, and quantity before placing the order. Avoids surprises when the invoice arrives, especially for purchases across time zones like London or Sydney with different VAT rules.
Converting a fixed coupon into an effective rate. A "$15 off $75" coupon is 20% off. Enter the values and the discount percentage calculator shows you the real rate — handy when comparing against a straight percent-off offer.
Retail math for small business pricing. Set a target margin by working the formula in reverse: enter your cost as the price and your markup as a negative discount to find break-even, then adjust from there.

Frequently asked questions

Why doesn't 20% off plus 10% off equal 30% off?

Because each discount applies to the price that remains after the previous one. On a $100 item, 20% off leaves $80; then 10% off $80 is $8 more — total savings $28, not $30. The effective combined discount is 28%, and this tool computes that correctly using the multiplicative formula: 1 − (1 − 0.20) × (1 − 0.10).

Does sales tax apply to the original price or the discounted price?

In virtually every U.S. jurisdiction, sales tax is applied to the final selling price after discounts — not the pre-discount sticker price. This calculator follows that rule. If you're unsure of your local rate, check your state's department of revenue website.

Is my data sent to a server when I use this tool?

No. The entire calculation runs in your browser using JavaScript — nothing is transmitted to any server. There are no accounts, no cookies tied to your inputs, and no logs. This is the same principle behind tools like offline password managers: the math happens locally, so there is nothing to intercept or leak. Unlike incidents such as Cloudbleed, where server-side processing exposed user data, client-side tools carry no equivalent risk.

What is the discount percent formula?

Discount % = (Original Price − Sale Price) ÷ Original Price × 100. Rearranged: Sale Price = Original Price × (1 − Discount % ÷ 100). For stacked discounts, apply the formula sequentially. You can verify any result with the RFC 4122-style principle of determinism: same inputs always produce the same output.

Can I use this as a discount and tax calculator together?

Yes. Enter the original price, your discount (percent or fixed), and your tax rate in the same form. The tool deducts the discount first, then computes tax on that reduced amount, and shows the grand total — matching how a point-of-sale system would ring it up.

How do I find the percentage off from two prices?

Subtract the sale price from the original price to get the discount value, then divide by the original price and multiply by 100. For example: ($80 original − $60 sale) ÷ $80 × 100 = 25% off. If you need to work with rates and ratios more broadly, the [percentage calculator](/en/percentage-calculator/) covers those cases.