Three numbers sit in one relationship: original price, discount percent, and sale price. If you have the original and the percent, the amount off is original × (percent ÷ 100) and the sale price is original minus that amount. If you have the sale price and the percent, the original is sale ÷ (1 − percent/100). If you have both prices, the percent off is (original − sale) ÷ original × 100.
The Discount Calculator performs the first of those three: original and percent in, amount and final price out. It rejects a negative price and a percent outside 0–100. It does not add tax, stack a second coupon, or parse a currency symbol. This guide is how discounts, sale prices, and original prices relate when you need the inverse, or when two discounts arrive in a row.
Example: 80 and 25% → 20 off, 60 to pay. That is the Discount Calculator’s Example pair. At 0% the sale equals the original. At 100% the sale is 0. If you only needed “what is 25% of 80” without calling it a price, the Percentage Calculator is the same arithmetic with different labels.
Example: a ticket says 60 after 25% off. 60 ÷ 0.75 = 80. If you then put 80 and 25% into the Discount Calculator, you should see 60 again. That loop is the check. The calculator will not run this inverse for you; do the division, then verify forward.
Example: 80 to 60 is 20 ÷ 80 = 25% off. That is a discount percent, not a percentage change story about some other base. If you need the signed change from 80 to 60 as a general quantity, that is −25% on the Percentage Change Calculator, and the comparison with difference and points lives in percentage change vs difference vs percentage points.
Two percents off in sequence multiply the remaining fractions. Twenty percent off, then ten percent off, is 0.8 × 0.9 = 0.72 of the original: 28% off in total, not 30%. The Discount Calculator applies one percent to the price you type. To model a stack, run the first final price through the form again as the new original, or multiply the remaining fractions by hand and then apply one combined percent.
A “further 10% off already reduced prices” sign is the second run. Adding the sticker percents is the usual mistake, and it overstates the saving.
It will not add sales tax, shipping, or a member rate. It will not accept 120% off. It will not read “$19.99.” Type 19.99. It will not force two decimal places, because not every figure people paste is money in one currency. It is not a store’s advertised-price policy.
A markup is the opposite direction: the original is the smaller number and you are asking what percent was added. Percent added = (new − original) ÷ original × 100. That is percentage change, not a markdown. Do not put a marked-up price into the Discount Calculator and expect it to invent a “percent on.” Use the Percentage Change Calculator for that pair, then come back here only if the story is still “percent off a list.”
Use this order: identify which two of the three numbers you have, compute the third with the matching identity, then confirm forward on the Discount Calculator when the missing number was the original or the percent. If the question was never about a price tag, do not force this page. Use the Percentage Calculator for a bare percent of an amount.
From a non-negative original price and a percent between 0 and 100, it shows the amount off and the final price. It does not add tax.
original = sale ÷ (1 − percent/100). A 25% off sale of 60 came from 60 ÷ 0.75 = 80.
Each percent applies to the current price. 0.8 × 0.9 = 0.72 of the original, which is 28% off in total.
Not on this tool. The percent must be 0–100. A 100% discount makes the final price 0.
