Calculating Discounts: Formula and Examples

A discount calculator works out how much is taken off an original price and, when needed, the price left to pay. Enter the original price and discount percentage; the calculator returns the discount amount and discounted price.

Formula

To find the discount amount, multiply the original price by the discount rate and divide by 100. Subtract the discount amount from the original price to find the price after the discount.

• Discount amount = original price × discount rate ÷ 100
• Discounted price = original price − discount amount

Here, price is the original price in the currency shown, and discount is the percentage rate. The outputs use that same currency. A percentage is a number of parts per 100: for example, 20% is 20 ÷ 100, or 0.20. An equivalent shortcut is discounted price = original price × (1 − discount rate ÷ 100).

Worked Example

Using the calculator’s default values, the original price is 100 currency units and the discount rate is 20%.

1. Discount amount = 100 × 20 ÷ 100 = 20.00 currency units.
2. Price after discount = 100 − 20 = 80.00 currency units.

The calculator therefore shows a discount amount of 20.00 and a discounted price of 80.00. The currency label is a placeholder: the same arithmetic applies whether the price is expressed in dollars, pounds, euros, or another currency.

How to Calculate a Discount

For a manual calculation, first identify the price the percentage applies to. Convert the percentage into a decimal by dividing it by 100, multiply by the applicable price to find the reduction, then subtract that reduction. For example, 15% of 60 is 60 × 0.15 = 9, so the price after a single 15% discount is 60 − 9 = 51.

You can also calculate the remaining percentage directly. A 15% discount leaves 85% of the original price, so 60 × 0.85 = 51. This is convenient for mental arithmetic, but it gives the final price rather than showing the amount saved. If you need both, calculate the reduction and subtract it.

Discounts can apply to more than one item. If every item has the same rate and all listed prices qualify, add the prices first and apply the rate to that total. If only some products qualify, calculate from their eligible subtotal instead. Shipping, fees, or other charges may be treated separately, so check what the stated discount covers.

Percentage Off Versus Money Off

A percentage discount depends on the original price; a fixed-amount discount subtracts the same number of currency units regardless of the item’s price. To compare offers, calculate each against the same eligible price. For a 50-unit item, 20% off saves 10 units, while 8 units off saves 8. For a 30-unit item, 20% off saves 6, so the fixed 8-unit reduction would be larger if it can be applied in full.

For a fixed reduction, the basic calculation is simply final price = original price − fixed discount. If that subtraction would make the result negative, the actual offer’s terms matter: a seller may cap the reduction at the price, impose a minimum purchase, or exclude certain items. Do not assume the offer can be used beyond its stated conditions.

Stacking Discounts and Rounding

Two percentage discounts applied one after another are generally calculated on successive prices, not added together. For example, with 100 as the starting price, 20% off reduces it to 80. Applying a further 10% reduction to 80 takes off 8, leaving 72. The combined reduction is 28% of the original price, not 30%.

That result can differ from offers that explicitly combine rates or apply each rate to the original price. The wording and order of the offer determine the calculation. A fixed-amount reduction combined with a percentage offer can also produce different results depending on which is applied first.

Calculations can produce fractions of the smallest currency unit. A displayed price is usually rounded to the currency’s customary precision, often two decimal places, but rounding policies can vary. When several items are involved, rounding each line separately may not match applying a discount to the combined subtotal and rounding once. The calculator displays two decimal places; its displayed figures are rounded, so tiny differences may occur if you compare rounded intermediate amounts with an unrounded calculation.

Common Mistakes and Limits

• Subtracting the percentage as a whole number: 100 minus 20 is not the correct way to calculate 20% off 100. First find 20% of 100, then subtract the resulting 20.
• Using the wrong starting price: A sale reduction applies to the price specified by the offer, which may not be a previous or advertised list price. Confirm the eligible original price.
• Adding sequential rates: Applying 20% and then 10% to the reduced balance leaves 72% of the original price, not 70%.
• Ignoring eligibility and extra charges: A simple percentage formula cannot determine whether an item qualifies or how checkout fees are handled. Those depend on the offer’s terms.

This calculator assumes a nonnegative original price and a discount rate entered as a percentage. It performs arithmetic only; it does not verify an offer, decide which products qualify, include taxes or fees, or determine a seller’s rounding and stacking rules. Use the calculation as an estimate of the price reduction, and check the final total shown by the seller.

Frequently Asked Questions

How do I calculate 20% off a price?
Multiply the original price by 0.20 to find the amount off, then subtract it. For a price of 50, the discount is 10 and the price after the discount is 40.

How do I find the original price before a discount?
Divide the discounted price by the fraction that remains. For example, if a price after 20% off is 80, divide 80 by 0.80 to get an original price of 100. This works when the discount rate and final price are known and no other changes are included.

How do I calculate the percentage discount?
Subtract the discounted price from the original price, divide the difference by the original price, and multiply by 100. If 80 is reduced to 68, the reduction is 12, and 12 ÷ 80 × 100 = 15%.

Are two 10% discounts the same as 20% off?
No, not when they are applied one after another. The first 10% leaves 90% of the price; the next takes 10% of that remainder. Together they reduce the original price by 19%.

Does the discount apply before or after tax?
There is no universal answer for every sale or jurisdiction. The offer’s terms and applicable tax rules determine how the taxable amount is calculated. This calculator does not calculate tax; check the seller’s itemized total and relevant local guidance.

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in price | Original price | currency | 100 | 0
in discount | Discount rate | % | 20 | 0
out saving | Discount amount | currency | price * discount / 100 | 2
out final | Price after discount | currency | price - saving | 2