DISCOUNT & CHANGE

Discount and Percentage Change Calculator

Calculate final price and savings from a discount, or the percentage change between two values. Handles a zero baseline safely and runs entirely in your browser.

Two modesZero-safeNo accountNot financial advice

Original price

Discount (%)

Enter a percentage or an amount, not both.

Discount amount

Final price

$80

Original price: $100
Discount (%): 20%
Discount amount: $20
Savings: $20

A 20% discount on $100 saves $20, for a final price of $80.

Formula

Final price (discount): Final = Original × (1 − Discount%)
Savings: Savings = Original − Final
Percentage change: Change% = ((New − Original) ÷ |Original|) × 100

Percentage change is undefined when the original value is zero (division by zero).
The denominator uses the absolute value of the original, so a change from −100 to 100 is a 200% increase.
If discount percentage and discount amount conflict, the percentage is used.

Discounts in retail and sales

A discount reduces an original price by a percentage or a fixed amount. Percentage discounts are common in retail promotions; fixed-amount discounts appear in coupons and rebates. This calculator handles both and shows the final price and total savings.

Percentage change in business reporting

Percentage change is the standard way to describe growth or decline: revenue up 12% year over year, costs down 5%, headcount up 8%. It compares the difference between two values to the starting value. When the starting value is zero, percentage change is undefined and the absolute difference should be reported instead.

Frequently asked questions

How is a discount calculated?

Final price = original price × (1 − discount %). Savings = original price − final price. You can enter either a discount percentage or a fixed discount amount.

How is percentage change calculated?

Percentage change = ((new value − original value) ÷ |original value|) × 100. A positive result is an increase; a negative result is a decrease. The denominator uses the absolute value of the original.

Why is percentage change undefined when the original is zero?

Division by zero is undefined. When the original value is zero, no percentage can represent the change. The calculator still shows the absolute difference.

Can I enter both a discount percentage and a discount amount?

Yes. If both are provided and consistent, the calculator uses the percentage. If they conflict, it uses the percentage and notes the inconsistency.

Is this financial advice?

No. This is a general-purpose calculator and is not financial, accounting, tax, legal, or business advice.

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No account. No ads. No tracking. Your calculation inputs stay in your browser and are not sent to WebF1 or stored on a server.

Built by WebF1 LLC

WebF1 LLC builds custom business systems, integrations, and practical software tools. This discount and percentage-change calculator is a free, private utility and is not financial, accounting, tax, legal, or business advice.

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