Sale tags love to shout “30% off” and leave the maths to you. This calculator does it in a couple of seconds. Type in the original price and the discount, and it shows what you’ll actually pay and how much you’re saving. It also covers the everyday percentage questions that come up away from the shop: what 15% of a number is, or how much something has gone up or down.
Choose what you want to work out: the price after a discount, a percentage of a number, or a percentage change.
Enter your numbers. For a discount, that means the original price and the percentage off.
Read the result. The final price and the amount saved appear side by side.
Decimals are fine, so a 12.5% discount works just as well as a round 10%.
Nothing exotic here, just four short formulas:
Discount amount = original price × (discount % ÷ 100)
Final price = original price − discount amount
Percentage of a number = number × (percent ÷ 100)
Percentage change = (new value − old value) ÷ old value × 100
A jacket on sale. The jacket costs $80 and is 25% off. 80 × 0.25 = 20, so you save $20 and pay $60.
A percentage of a number. What is 15% of 240? 240 × 0.15 = 36.
A change over time. Your rent went from $900 to $990. The difference is $90, and 90 ÷ 900 = 0.10, so rent rose by 10%.
“20% off, then an extra 10% off” sounds like 30% off. It isn’t. The second discount applies to the price that’s already been reduced. Take a $100 item: 20% off brings it to $80, and 10% off that brings it to $72. You saved 28%, not 30%.
To check a deal like this, run the calculator twice and use the first result as the new original price.
Up and down aren’t symmetrical. A price that rises 50% and then drops 50% doesn’t return to where it started. $100 becomes $150, then $75.
Check where tax comes in. In most places the discount is taken off first and tax is added to the lower price, but not every shop works that way. The receipt is the final word.
“Up to 50% off” is a ceiling, not a promise. It usually applies to a handful of items, not the whole store.
How can I work out a discount in my head?
Find 10% by moving the decimal point one place to the left, then build from there. For 30% off a $60 item, 10% is $6, so 30% is $18 and the price drops to $42. For 5%, take half of the 10% figure.
Does the same formula work for a decrease?
Yes. If the percentage change comes out negative, the value went down. A result of −20% means a 20% drop.
Can I use any currency?
Yes. The calculator only works with numbers, so dollars, euros, dirhams or anything else gives the same percentages.
What if the discount is 100% or more?
At 100% the item is free. Anything above that doesn’t make sense for a discount, so double-check the number you entered.
Why doesn’t my result match the price in the shop?
Shops often round to the nearest cent or end a price in .99, and some add taxes or fees after the discount. Small differences are normal.
Results are for guidance only. Always confirm the final price at checkout.