Percentages: Discounts vs Change

Published 2026-10-10 · Updated 2026-10-14

Ready to try it? Open Percentage calculator and follow the example below.

Pick the right operation for discounts, increases and comparisons.

Choose the reference amount

A percentage describes a portion relative to a base. Twenty percent of 150 is 30 because 150 is the reference amount. Before calculating, identify whether you need the portion itself, the final discounted amount or the change between two values.

Calculate a discount

For an item priced at 150 with a 20% discount, subtract 30 to get 120. A second discount applies to the new amount when the seller uses successive discounts. Another 10% off 120 gives 108, so the combined reduction is 28%, not 30%.

Distinguish change from difference

A rise from 80 to 100 is an increase of 25% relative to 80. A fall from 100 to 80 is a decrease of 20% relative to 100. The starting value changes the answer. A percentage change from zero is not defined by the usual formula because it would require division by zero.

Use the matching mode

Open the percentage calculator, select the operation and check the field labels. Enter plain numbers rather than adding currency signs. Compare the result with a rough estimate. For shopping, confirm whether taxes, shipping and other charges are included in the amount you are calculating.

Worked example: A discount and its reversal are different

A 20% discount on 100 removes 20 and leaves 80. Increasing 80 by 20% adds 16, producing 96 rather than 100. Returning from 80 to 100 requires a 25% increase, because the increase is measured against 80. When comparing offers, identify the reference value before entering a percentage. If a price already includes another discount or tax, write down the calculation order. A correct formula applied to the wrong starting price still gives the wrong decision.

A discount and its reversal are different: check input, use the tool, then review output — Use a known example and inspect the result before sharing it.

Try this workflow

Choose the percentage operation that matches your question.
Read the current field labels and enter the relevant original value and percentage or new value.
Calculate and review whether the output is an amount, final price or percentage.

Choose percentage of a number, percentage change or discount. Percentage change needs a non-zero original value. Discounts must be from 0–100%. A change from a negative starting value needs careful interpretation; always keep the original figures alongside the answer.

Continue with a related task

Try it free

Percentage calculator needs no signup. Check its limits, use a non-sensitive example, and keep the original before saving a changed file.