Mental discount math helps you judge a sale before reaching the checkout. The goal is a reliable estimate; use the calculator when you need the exact cents.
Find the discount, then subtract
For 20% off $70, first find 10% ($7), double it ($14), then subtract $14 from $70. The sale price is $56.
Use quarters for 25%
Twenty-five percent is one quarter. A 25% discount on $84 is $84 ÷ 4 = $21. Subtracting gives a sale price of $63.
Break unusual percentages into pieces
For 35% off $60, combine 30% ($18) and 5% ($3). The discount is $21 and the sale price is $39.
Use the amount you pay instead
Sometimes it is faster to calculate the remaining percentage. With 40% off, you pay 60%. Sixty percent of $50 is $30.
A calculator is often the quickest way to check your mental math. The important part is using the right starting value.
Open a calculator →Common questions
What does 30% off mean I pay?
You pay 70% of the original price.
How do I estimate 15% off?
Find 10%, add half of that for 5%, then subtract the total.
Should tax be calculated before or after a discount?
That depends on local rules and the type of discount; check the checkout total for the exact amount.
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