How to Calculate a Discount Percentage and Final Sale Price
Seeing "20% off" or "30% discount" on a product is common, but calculating the actual amount you will pay is not always obvious. A quick discount calculation can tell you how much money you are saving and what the final sale price will be.
The good news is that the basic formulas are simple. Once you know the original price and discount percentage, you can calculate the discount amount and final price in just a few steps.
What Is a Discount Percentage?
A discount percentage tells you how much a price has been reduced from its original amount.
For example, if a jacket originally costs $100 and is advertised at 20% off, the discount is 20% of $100.
The discount amount is:
$100 × 20 ÷ 100 = $20
So, you save $20.
The final sale price is:
$100 − $20 = $80
In other words, a 20% discount on a $100 item gives you a final price of $80.
Discount Percentage Formula
The basic formula for finding the discount amount is:
Discount Amount = Original Price × Discount Percentage ÷ 100
Once you have the discount amount, subtract it from the original price:
Final Sale Price = Original Price − Discount Amount
You can combine both steps into one formula:
Final Sale Price = Original Price × (1 − Discount Percentage ÷ 100)
This second formula is especially useful when you want to calculate the final price quickly.
How to Calculate a Discount Step by Step
Suppose a pair of shoes has an original price of $150 and the store is offering 25% off.
First, calculate the discount:
$150 × 25 ÷ 100 = $37.50
The discount amount is $37.50.
Next, subtract the discount from the original price:
$150 − $37.50 = $112.50
The final sale price is $112.50.
This same method works for clothing, electronics, groceries, hotel bookings, subscriptions, and many other purchases.
How to Calculate 10%, 20%, 30%, or 50% Off
Some discounts can be calculated mentally quite easily.
For a 10% discount, move the decimal point one place to the left. For example, 10% of $80 is $8.
For a 20% discount, calculate 10% and double it. On an $80 item, 20% is $16, making the sale price $64.
For a 30% discount, calculate 10% and multiply it by three. A $200 product would have a $60 discount and a final price of $140.
A 50% discount means paying half the original price. An item priced at $120 would cost $60 after a 50% discount.
These shortcuts are useful when comparing products while shopping.
How to Calculate the Original Price From a Sale Price
Sometimes you know the discounted price but want to find the original price.
For example, suppose an item costs $72 after a 20% discount.
After a 20% discount, you are paying 80% of the original price.
So:
Original Price = Sale Price ÷ (1 − Discount Percentage ÷ 100)
Using the example:
$72 ÷ 0.80 = $90
The original price was $90.
This is different from simply adding 20% to $72. Percentage discounts and percentage increases are not interchangeable.
How to Find the Discount Percentage
You may also have the original price and sale price but not know the percentage discount.
For example, a product was originally $250 and is now $200.
First, find the amount saved:
$250 − $200 = $50
Then calculate the percentage:
Discount Percentage = Discount Amount ÷ Original Price × 100
So:
$50 ÷ $250 × 100 = 20%
The product was discounted by 20%.
What About Multiple Discounts?
Stores sometimes advertise discounts such as "20% off plus an extra 10% off." These discounts are usually applied one after another rather than simply adding them together.
For example, a $100 item with 20% off becomes $80.
An additional 10% discount is then taken from $80:
$80 × 10 ÷ 100 = $8
The final price is $72.
The total saving is $28, which is a 28% reduction from the original $100—not 30%.
This is an important detail when comparing promotional offers.
Do Sales Tax and Discounts Work Together?
Depending on the store and local tax rules, sales tax may be calculated after the discount is applied.
For example, if a $100 product receives a 20% discount, the discounted price is $80. If a 5% tax is then applied:
$80 × 5 ÷ 100 = $4
The total would be $84.
However, tax rules vary by location and transaction type, so the exact calculation can differ.
Common Discount Calculation Mistakes
One common mistake is calculating the discount percentage from the sale price instead of the original price. The discount percentage normally refers to the original price.
Another mistake is adding two separate discounts together. A 20% discount followed by 10% off is not necessarily the same as a 30% discount.
It is also easy to forget that taxes, shipping charges, coupons, or other fees may be added separately. The advertised sale price may not always be the final amount shown at checkout.
When comparing deals, look at the actual final price rather than focusing only on the percentage displayed in the advertisement.
Frequently Asked Questions
How do I calculate a discount percentage?
Multiply the original price by the discount percentage and divide by 100. The result is the discount amount. Subtract that amount from the original price to get the final sale price.
How do I calculate 20% off a price?
Multiply the original price by 20 and divide by 100. Then subtract the result from the original price. For example, 20% off $50 is $10, so the final price is $40.
How do I calculate the final sale price?
Use this formula:
Final Sale Price = Original Price × (1 − Discount Percentage ÷ 100)
For a $200 item with a 25% discount, the final price is $150.
How do I find the original price from a discounted price?
Divide the sale price by the percentage you are paying after the discount. For example, after 20% off, you are paying 80%, so divide the sale price by 0.80.
Are two discounts added together?
Usually, no. Multiple discounts are often applied separately. A 20% discount followed by another 10% discount results in an overall saving of 28%, not 30%.
