Business & Finance
Published September 17, 2025 · Updated August 2, 2026
To calculate a discount, multiply the original price by the discount as a decimal to find the saving, then subtract it. Faster: multiply the original price by (1 - discount). A $250 item at 20% off saves $50 and costs $200.
To calculate a discount, multiply the original price by the discount percent to find savings, then subtract savings from the original price. Shortcut: Final price = Original price x (1 - Discount % / 100).
Example: $150 at 30% off gives $45 savings and a $105 sale price. For instant final sale price math, use the Discount Calculator.
Sales and discounts are everywhere, from "25% Off" signs at your favorite store to online coupon codes and Black Friday doorbusters. But how do you quickly figure out what you're actually saving and what the final price will be? This guide walks you through every situation you'll meet at the checkout - basic percent off, adding sales tax, stacking two discounts, working backwards to the original price, and deciding whether "% off" or "$ off" is the better deal.
Calculating a discount is a straightforward, two-step process. All you need is the original price and the discount percentage.
First, convert the discount percentage to a decimal by dividing it by 100. Then, multiply this decimal by the original price.
Amount Saved = Original Price x (Discount % / 100)
For example, for a $150 item with a 30% discount: Amount Saved = $150 x 0.30 = $45.
Simply subtract the amount you saved from the original price to find the final price you'll pay.
Final Price = Original Price - Amount Saved
Continuing our example: Final Price = $150 - $45 = $105.
If you only need the final price, you can do it in one step. If an item is 30% off, it means you are paying 70% of the original price (100% - 30%).
Final Price = Original Price x (1 - (Discount % / 100))
Using our example: Final Price = $150 x (1 - 0.30) = $150 x 0.70 = $105.
Why do the math yourself? Our Discount Calculator gives you the final price and your total savings in seconds - plus a percent-off chart for common prices.
Use the Discount Calculator →A common homework and real-world question: "A backpack costs $50, it's 20% off, and sales tax is 8% - what's the total bill?" The key rule is that tax is charged on the discounted price, not the original price. So you always discount first, then add tax.
The shortcut: multiply the discounted price by 1 + tax rate (1.08 for 8%, 1.05 for 5%, and so on). If you want to separate out the tax portion of any purchase, our VAT / GST & Sales Tax Calculator does it instantly.
When a store offers a second discount on top of the first, you cannot simply add the percentages. Each discount applies to the running price, so the discounts compound.
Take a $100 jacket at "20% off, plus an extra 10% at the register":
The true combined discount is 28%, not 30%. Stacked discounts always come out a little smaller than the sum - a useful thing to know before you assume a deal is better than it is.
Sometimes you see only the sale price and want to know the original - for example, to verify a "70% off" claim is genuine. To reverse a discount, divide the sale price by (1 - discount):
Original Price = Sale Price / (1 - (Discount % / 100))
If a sweater rings up at $72 after a 20% discount, the original price was $72 / 0.80 = $90. If the tag claimed a much higher "was" price than that, the markdown isn't what it seems.
Stores love to mix percentage and flat-dollar discounts because shoppers struggle to compare them on the spot. The trick is to find the break-even price. A flat $25 off equals 30% off only when the item costs about $83, because 30% of $83 is about $25.
When in doubt, calculate both final prices and compare - never assume the bigger-looking number is the better deal.
Big sale events are where discount math really pays off. Before you buy:
Multiply the original price by (1 minus the discount as a decimal). For 20% off $250: $250 x 0.80 = $200. The saving is the difference, $50. For a 15% discount you would multiply by 0.85, and so on.
Percent off and discount mean the same thing. Divide the saving by the original price and multiply by 100 to go the other way. Saving $50 on a $250 item is $50 / $250 x 100 = 20% off.
Original price x (1 - discount). An $880 television at 30% off is $880 x 0.70 = $616, a saving of $264. The same single step works for any percentage.
Apply the discount first, then add tax to the reduced price. A $250 item at 20% off is $200, and 8% sales tax on $200 adds $16, giving $216. Tax is charged on what you actually pay, not the pre-discount price.
Divide the sale price by (1 minus the discount). An item selling for $200 after 20% off was originally $200 / 0.80 = $250. Dividing by the discount itself, or adding the percentage back, both give the wrong answer.
They multiply, they do not add. A 30% discount followed by an extra 20% off is 0.70 x 0.80 = 0.56, so you pay 56% of the original and save 44%, not 50%. A $250 item ends at $140.
Take 10% by moving the decimal one place left, then double it. On $250, 10% is $25, so 20% is $50, and the sale price is $200. For 15%, take 10% and add half of it again.
No, multiplication is commutative, so applying an 8% tax before or after a 20% discount gives $216 either way. What matters legally is that tax is calculated on the discounted amount, which is what retailers do.
Knowing how to calculate discounts on the fly helps you make smarter purchasing decisions, verify that sale prices are honest, and truly understand the value you're getting. Bookmark our Discount Calculator for instant answers, and pair it with the Markup Calculator if you set prices yourself - it's a small skill that quietly saves real money every time you shop. For official guidance on this topic, see the CFPB's consumer finance tools.
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