How to Calculate a Discount and Percentages Quickly (With Examples)
Work out the sale price, how much you save and a percentage of any number. Includes second discounts and adding tax.
Sales signs say "30 percent off", "extra 10 percent off" or "buy now, save 500". Knowing the real price quickly helps you decide whether a deal is genuinely good. The maths is simple once you know the pattern, and the free Discount Calculator does it for you.
Quick answer
Enter the original price and the discount percent. If there is a second discount, enter it too, and add tax if you want to see the final price at the till. You see the sale price and how much you save.
The basic formula
Sale price = original price x (1 - discount percent / 100)
Examples:
- 2,000 with 25 percent off: 2,000 x 0.75 = 1,500. You save 500.
- 3,500 with 40 percent off: 3,500 x 0.60 = 2,100. You save 1,400.
- 899 with 15 percent off: 899 x 0.85 = 764.15.
A quick mental shortcut: 10 percent is the number with the decimal point moved one place; 5 percent is half of that; 25 percent is a quarter.
Two discounts are not added together
This is the most common mistake. "20 percent off, plus an extra 10 percent off" is not 30 percent. The second discount applies to the already reduced price:
- Original 1,000.
- After 20 percent off: 800.
- After an extra 10 percent off 800: 720.
- The total discount is 28 percent, not 30.
The calculator has a second-discount field for exactly this reason.
Adding tax or VAT
A price on a shelf may or may not include tax. If you want the full amount at the till, add the tax rate to the discounted price. For example, a sale price of 720 with 20 percent VAT added is 864. The VAT Calculator can also take tax out of a price that already includes it.
How to use the calculator, step by step
- Open the Discount Calculator.
- Enter the original price.
- Enter the discount percent.
- If there is a second discount, enter it.
- Add sales tax or VAT if you want the price at the till.
- Read the final price and the amount saved.
Other percentage questions
Not every question is about a discount. The Percentage Calculator handles three common ones:
- What is X percent of Y? (a tip, a commission)
- What percent is X of Y? (marks, a share of a total)
- What is the percentage change between two numbers? (growth, price increase)
Tips for smart shopping
- Compare the final price, not the percentage. A larger percentage off a higher starting price may still cost more.
- Check the original price is real. Some shops raise prices before a sale.
- Include delivery and tax when comparing online offers.
- Watch for minimum spends that make a "discount" cost more.
More percentage skills for daily life
Finding the original price
A shirt costs 1,200 after a 20 percent discount. What was the original price? Divide by 0.80: 1,200 / 0.80 = 1,500. A frequent mistake is to add 20 percent to 1,200, which gives 1,440 and is wrong, because the 20 percent was taken from the larger original.
Percentage increase
A price rises from 800 to 920. The increase is 120, and 120 / 800 = 15 percent. Always divide by the starting value.
Percentage points versus percent
If an interest rate moves from 5 percent to 6 percent, it rose by 1 percentage point, which is a 20 percent increase in the rate. The two are easily confused in news and advertising.
Splitting a bill with tip
A bill of 2,400 with a 10 percent service charge is 2,640. Shared among 4 people, each pays 660.
How shops use percentages
- "Up to 70 percent off" means only a few items reach 70 percent. Most are lower.
- "Buy one get one free" is a 50 percent discount on two items.
- "Flat 500 off on 3,000" is 16.7 percent, which you can compare with percentage offers.
- Cashback is not a price reduction at the till. Check when and how it is paid.
Check before you buy
- Find the real price after all discounts and tax.
- Compare the unit price, such as price per kilogram or per metre.
- Look at the seller's reputation and return policy.
- Decide if you needed it anyway. A discount on something you do not need is still spending.
Percentages in study and work
Percentages appear in exam marks, growth rates, commission and savings. The Percentage Calculator answers the three most common questions in seconds, and the Margin and Markup Calculator helps sellers set profitable prices.
Quick checklist
- Calculate the final price, not only the percentage.
- Remember that two discounts compound.
- Add tax or delivery.
- Compare with other shops.
A worked example: comparing two offers
Two shops sell the same phone. Shop A lists it at 24,000 with 10 percent off and free delivery. Shop B lists it at 22,000 with 5 percent off and a delivery charge of 300. In Shop A the final price is 24,000 x 0.90 = 21,600. In Shop B it is 22,000 x 0.95 = 20,900, plus 300 for delivery, making 21,200. Shop B is cheaper by 400, even though its percentage discount is smaller. Without calculating, many shoppers would have chosen Shop A for the bigger "10 percent off".
Rules of thumb
- Always compare final prices.
- Include delivery and tax.
- Check warranty and returns, which have value.
- Beware of fake "original" prices.
Frequently asked questions
How do I take 20 percent off a price? Multiply the price by 0.80.
Is a 20 percent plus 10 percent discount equal to 30 percent? No. The second one applies to the reduced price, so it is 28 percent in total.
How do I find the original price from a sale price? Divide the sale price by (1 - discount percent / 100).
Can I add tax too? Yes. The calculator can add sales tax or VAT.
Is it free? Yes.
How do I add a percentage to a number? Multiply by (1 + percent / 100). For 15 percent, multiply by 1.15.
Why is 20 percent off then 20 percent on not equal? Because the second percentage is applied to a different base.
What is a percentage point? The simple difference between two percentages, not a relative change.
How can I check a discount quickly in my head? Find 10 percent by moving the decimal point, then add or subtract multiples.
Is a bigger percentage always a better deal? No. A smaller percentage on a lower starting price can be cheaper.
Next step
Open the Discount Calculator below and check the next sale price before you buy.