Discount Calculator

WHAT IT DOES

Discount Calculator helps you figure out exactly how much you will pay after discounts and taxes. Enter the original price, a discount percentage, and a tax rate — the panel instantly shows the discounted subtotal, tax amount, final price, and total savings. Need to apply multiple discounts? Add additional discount tiers for scenarios like store discounts combined with coupon codes or seasonal promotions. Choose from three rounding options: nearest cent, nearest dollar, or no rounding, so you can match your preferred currency format.

WHERE IT RUNS

This script runs on every website you visit. Whether you are shopping on e-commerce sites, comparing prices across retailers, working with invoices in accounting software, or calculating budgets in a spreadsheet application, the panel is always accessible. It stays out of your way until you need it, floating conveniently on the page.

HOW TO USE

Enter the original price in the first field and the discount percentage in the second. The results update automatically as you type. Add a tax rate percentage if applicable. To apply additional discounts, click "Add Discount Tier" and enter each extra discount percentage — the calculation applies them sequentially. Select your preferred rounding method from the dropdown. The panel remembers your default tax rate and rounding preference across sessions. Click the "Copy Result" button to copy the final price to your clipboard. Every calculation is saved to a history list that you can click to reuse previous values.

THE COMPOUND DISCOUNT MECHANISM

Most simple discount tools apply all discounts additively (e.g., 20% + 10% = 30%), which overestimates savings. Discount Calculator applies multiple discounts sequentially, matching how real retail works. If a store offers 20% off and you have a 10% coupon, the calculation applies 20% to the original price, then 10% to the reduced price. This yields an effective discount of 28%, not 30%, giving you accurate final prices. The additional discount tiers are applied in the order they appear, allowing you to experiment with different discount stacking scenarios.

THE PANEL

The panel is fully draggable and remembers its position per site. It minimizes to a compact floating bubble when collapsed. All settings — default tax rate, rounding preference, and calculation history — persist across browser sessions using GM_setValue storage. Press the Escape key to close the panel. The panel automatically focuses the first input field for keyboard-first workflows.

PLEASE NOTE

This script requires the free BotGentz extension to run. Websites change their structure and behavior over time; if a particular checkout page stops working with the copy functionality, the script may need an update. No user data is sent anywhere — all calculation history and settings are stored locally in your browser. The script never reads or modifies password, hidden, or file input fields.