Discount & Percent Calculator
Instantly compute discounted price, tax in/out, "what percent", and rate of change. Live results.
About this tool
This percent and discount calculator handles the everyday and work calculations that involve percentages, grouped by purpose and computed the moment you type. It covers the discounted price, tax-inclusive and tax-exclusive amounts, the ratio "what percent of Y is X," and the rate of increase or decrease between two numbers. Everything runs in your browser, so the values you enter are never sent to a server.
Percentages are simple in principle, but the multiplication or division changes with each situation β "what is 20% off," "what is the pre-tax amount of a tax-included 1,100 yen," "how many percent up from last month" β and that makes them easy to get wrong in your head. This tool separates the inputs by purpose so you reach the right calculation without confusion.
Discount mode gives you the amount to pay and the amount saved from an original price and a discount rate. Tax mode converts between tax-exclusive and tax-inclusive amounts. Ratio mode computes "what percent of Y is X," and change mode computes "what percent did it change from A to B." It works for everything from checking a shopping discount to tracking month-over-month sales or traffic.
Values that vary by region or product, like tax rates, should be entered to match your situation (for example, reduced-rate items use a different tax rate). Because percentage results can differ by a unit depending on rounding (round or truncate), it is best to make a final check of official amounts such as invoices against the rounding rules you must apply.
How to use
- In "Discounted price", enter the price and discount (%) to get the final amount.
- "Tax included/excluded" converts both ways: enter price and tax rate (%), then pick a direction.
- "What percent" and "Rate of change" also update live as you type.
FAQ
Are the numbers I enter sent to a server?
No. All calculation is done in your browser, so the values you enter never leave your device.
How is "20% off" calculated?
The amount to pay is the original price minus the discount portion. For example, 20% off 1,000 is 1,000 minus 200, or 800. The tool shows both the amount to pay and the amount saved.
Can it compute tax-inclusive from tax-exclusive, or the reverse?
Yes. You can find the tax-inclusive amount from a tax-exclusive figure, or work back to the tax-exclusive amount from a tax-inclusive one. Enter the tax rate and switch as needed.
When would I use "what percent of Y is X"?
Use it to see how one value compares to a baseline β a progress rate toward a goal, a share of a total, or a test score percentage.
How do I find a rate of change (vs. last month or last year)?
Enter the before and after values and it computes the percentage increase or decrease. Handy for tracking sales, traffic, or weight over time.
How is rounding handled?
Ratio calculations produce decimal fractions, and the display is rounded to a set number of digits. Where a single unit matters, such as an invoice amount, make a final check using the rounding rule you must apply.