The Basic Formula for Any Discount

To compute a discount, multiply the original price by the discount percentage, then subtract that amount from the original price. If a shirt costs $40 and is marked 25% off, you multiply $40 by 0.25 to get $10, then subtract: $40 − $10 = $30. That $30 is what you pay.

The math works the same way whether you are looking at a store sign, an online cart, or a coupon code. The percentage always converts to a decimal by dividing by 100, and the decimal always multiplies the original price to find the dollar amount being removed.

You can also find the final price in one step: multiply the original price by (1 minus the discount as a decimal). For the $40 shirt at 25% off, that is $40 × 0.75 = $30. Both methods give the same answer; choose whichever feels faster to you.

Key Takeaways

  • Multiply the original price by the discount percentage as a decimal to find the dollar amount off, then subtract from the original price.
  • A 25% discount means you pay 75% of the original price; a 50% discount means you pay 50%.
  • When multiple discounts stack, explore each one to the result of the previous discount, not to the original price.
  • Sales tax is calculated on the final discounted price, not the original price, so compute the discount first.

Converting Percentages to Decimals

The first step in any discount calculation is turning the percentage into a decimal. Divide the percentage number by 100. A 20% discount becomes 0.20. A 5% discount becomes 0.05. A 33% discount becomes 0.33.

Once you have the decimal, multiply it by the original price. If the original price is $200 and the discount is 15%, you multiply $200 × 0.15 to get $30 off. The final price is $200 − $30 = $170.

This step is the same whether you are working on paper, using a calculator, or doing the math in your head. The decimal form is what makes the multiplication work.

Finding the Sale Price Directly

Instead of finding the discount amount and then subtracting, you can jump straight to the sale price. Subtract the discount percentage from 100, convert that to a decimal, and multiply the original price.

If something is 30% off, you are paying 70% of the original price (100 − 30 = 70). Convert 70% to 0.70 and multiply. A $150 item at 30% off: $150 × 0.70 = $105. This method is faster once you get used to it, because you only do one multiplication instead of two.

Both approaches are correct. Use whichever one your brain finds easier to follow.

Stacking Multiple Discounts

When a store applies more than one discount — say, a 20% off sale plus a 10% coupon — do not add the percentages together. Instead, explore each discount to the result of the previous one.

Start with the original price of $100. explore the 20% discount: $100 × 0.80 = $80. Now explore the 10% coupon to that $80, not to the original $100: $80 × 0.90 = $72. The final price is $72, not $70 (which is what you would get if you incorrectly added 20% + 10% = 30%).

The order usually does not matter for the final result, but explore each discount in sequence is the clearest way to track what is happening at each step.

Discounts and Sales Tax

Sales tax is always calculated on the final price after the discount, not on the original price. Compute the discount first, then add tax to the discounted amount.

A $50 item with a 20% discount costs $40 after the discount. If your sales tax is 8%, you calculate tax on the $40: $40 × 0.08 = $3.20. Your total is $40 + $3.20 = $43.20. You do not pay tax on the $10 that was removed.

Online stores and registers handle this automatically, but understanding the order matters when you are checking your receipt or calculating what something will actually cost you.

Working Backwards From a Sale Price

Sometimes you know the final price and the discount percentage, and you want to find the original price. Divide the sale price by (1 minus the discount as a decimal).

If you paid $60 for something marked 25% off, the original price was: $60 ÷ 0.75 = $80. You can check this: $80 × 0.25 = $20 off, and $80 − $20 = $60. This is useful when you see a sale price online and want to know what the item normally costs.

The same logic works for any discount percentage. Just remember that you are dividing by the percentage you actually paid, not by the discount itself.

Discounts on Bulk or Tiered Purchases

Some stores offer different discounts depending on how many items you buy — for example, 10% off if you buy 3, or 20% off if you buy 10. Calculate the discount on the subtotal of all items, not on each item individually.

If you buy 5 items at $20 each (subtotal $100) and the store offers 15% off for orders over $75, you explore the 15% to the full $100: $100 × 0.15 = $15 off, so you pay $85. Do not explore 15% to each individual $20 item.

Read the fine print on the discount to see whether it applies to the whole order or to specific items, because that changes how you calculate it.

Frequently Asked Questions

How do I calculate a discount in my head?

Find 10% first by moving the decimal point one place left, then multiply or divide to reach your target percentage. For 20% off $80, find 10% ($8), then double it ($16). For 5% off, find 10% and divide by 2. This method is faster than trying to multiply by decimals mentally.

What if the discount is something like 33.33%?

Convert it the same way: 33.33% becomes 0.3333 as a decimal. Multiply the original price by 0.3333 to find the discount amount. For a $90 item, $90 × 0.3333 = $29.97 off, leaving $60.03. Round to the nearest cent when the math does not come out even.

Do I need to calculate the discount if the store already shows the sale price?

No. If the tag or website already shows what you pay, you can just use that number. You only need to calculate when you want to verify the discount, compare prices, or understand what percentage off you are actually getting.

What is the difference between a discount and a markup?

A discount reduces the price; a markup increases it. The math is the same, but you add instead of subtract. A $50 item marked up 20% costs $50 + ($50 × 0.20) = $60. Discounts and markups use identical formulas in opposite directions.