How to Calculate Percent Off: Formula and Examples

To calculate percent off, multiply the original price by the discount percentage expressed as a decimal, then subtract that amount from the original price. For example, 20% off a $100 item means you save $20 and pay $80. The formula is: Sale Price = Original Price x (1 minus Percent Off / 100).

Percent off is one of the most common discount formats in retail, e-commerce, and seasonal sales. It tells you how much of the original price is subtracted, not how much you pay. If something is 25% off, you pay 75% of the original price. The "off" percentage and what you pay always add up to 100%.

This guide covers the percent off formula, quick mental math shortcuts, stacked discounts, sales tax rules, reverse calculations, and common mistakes. Updated August 2026.

Percent off formula and worked examples

The percent off formula is simple: Sale Price = Original Price x ((100 minus Percent Off) / 100). You can also write it as Original Price x (1 minus Percent Off / 100). The amount you save is Original Price x (Percent Off / 100).

Here is how the math works on real prices:

The first two rows are single discounts. The last two rows are stacked discounts, which we explain below. The examples match the calculations published by calculator.net and percentoffcalculator.org.

How do you calculate percent off quickly?

The fastest way to calculate percent off is to multiply the original price by the remaining percentage as a decimal. For 25% off, multiply by 0.75. For 40% off, multiply by 0.60. For 50% off, multiply by 0.50, which is the same as halving the price.

Here are the common multipliers:

• 10% off: multiply by 0.90
• 20% off: multiply by 0.80
• 25% off: multiply by 0.75
• 30% off: multiply by 0.70
• 40% off: multiply by 0.60
• 50% off: multiply by 0.50
• 75% off: multiply by 0.25

For example, a $80 item at 25% off costs $80 x 0.75 = $60. A $120 item at 30% off costs $120 x 0.70 = $84. This shortcut works because the discount percentage and the remaining percentage always add up to 100.

How do stacked discounts work?

Stacked discounts apply sequentially, not additively. Each new discount is calculated on the price after the previous one, not on the original price. So 20% off followed by 10% off is not 30% off. It is 28% off.

Here is the math on a $100 item:

1. First discount: $100 x 0.80 = $80
2. Second discount: $80 x 0.90 = $72
3. Effective total discount: 28%, not 30%

This is how checkout pages actually compute stacked offers. A store coupon and a promo code each apply to the price that remains after the previous discount. The layers multiply rather than add. Two 50% discounts in a row give 75% off, not 100% off.

"Stacking is multiplicative: 20% off followed by 10% off is not 30% off. It is 1 minus (0.80 x 0.90) = 28%." - CleverCalculator methodology

If you see a sign that says "20% off, plus an extra 10% off with code," the total discount is 28%, not 30%. Always apply the discounts in the order the store specifies, because the order can change the final price when the percentages differ.

How does sales tax affect percent off?

In most US states, sales tax is charged on the discounted price, not the original price. The retailer applies the discount first, then calculates tax on the new lower amount. This means a percent off discount also reduces the tax you pay.

For example, a $100 item with a 20% off promo and an 8% sales tax becomes $80 + $6.40 = $86.40. The tax is calculated on $80, not on $100. The order at checkout is: list price, minus all discounts and store coupons, equals the taxable amount, then tax is added.

Some jurisdictions require stores to display the original price, the discount percent, and the final sale price inclusive of all taxes. The National Institute of Standards and Technology (NIST) publishes a reference list of US retail pricing laws by state under the title "U.S. Retail Pricing Laws and Regulations by State."

How do you reverse calculate the original price?

If you know the sale price and the discount percentage, you can find the original price by dividing the sale price by the remaining percentage as a decimal. The formula is: Original Price = Sale Price / (1 minus Percent Off / 100).

For example, if the sale price is $60 after a 25% discount, the original price is $60 / 0.75 = $80. If the sale price is $72 after a 28% effective discount, the original price is $72 / 0.72 = $100.

This reverse calculation is useful when you want to check whether a store's "original price" is genuine, or when you need to compare the real discount across different retailers. It also helps when comparing vehicle prices such as the Honda Rebel 300 India price or the Pulsar N160 price after dealer discounts.

Percent off vs percent of: what is the difference?

Percent off tells you how much is subtracted from the price. Percent of tells you what portion of the price you pay. They are two sides of the same coin. If an item is 25% off, you pay 75% of the original price. The two numbers always add up to 100%.

This distinction matters when you compare deals. A "30% off" sign and a "pay 70% of the price" sign describe the same deal, but shoppers often misread one for the other. Always convert the discount to the remaining percentage before you multiply.

Common percent off mistakes to avoid

The most common mistake is adding stacked discounts instead of multiplying them. A second common mistake is applying tax to the original price instead of the discounted price. A third mistake is using the wrong multiplier, such as multiplying by 0.25 for 25% off instead of 0.75.

To avoid these errors, use a percent off calculator or write out the formula before you compute. The math is simple, but the order of operations matters. Whether you are checking the Tesla Model Y price in India or the electric scooter price in Pakistan, the same discount math applies.

Frequently asked questions

How do I calculate 20% off a price?

Multiply the original price by 0.80. For example, 20% off $50 is $50 x 0.80 = $40. You save $10.

What is the difference between percent off and a discount?

Percent off is a discount expressed as a percentage of the original price. A discount can also be a fixed amount, such as $10 off. Percent off is one specific type of discount.

How do I calculate the original price from a sale price?

Divide the sale price by the remaining percentage as a decimal. If the sale price is $60 after 25% off, the original price is $60 / 0.75 = $80.

Do stacked discounts add up?

No. Stacked discounts apply sequentially. 20% off followed by 10% off is 28% off, not 30% off. Each discount applies to the price after the previous one.

Is sales tax applied before or after the discount?

In most US states, sales tax is applied after the discount. The tax is calculated on the discounted price, which also reduces the tax you pay.

Use a percent off calculator

If you want to avoid manual math, several free percent off calculators handle single discounts, stacked discounts, sales tax, and reverse calculations. These tools are free, instant, and work on any phone or laptop.

Open the percent off calculator

Try the stacked discount calculator

Use the reverse percent off tool