How to Calculate a Discount (Free, With Simple Formulas)
"30% off" sounds great, but what do you actually pay? Calculating a discount is quick once you know the formula, and it helps you spot real deals and avoid overpaying. This guide shows how to calculate a discount and the final sale price, with worked examples and a free calculator.
🏷️ Try the Percentage Calculator now — freeOpen →Knowing the real price behind a percentage off helps you budget, compare deals, and catch when a "sale" isn't much of one. It's everyday math that saves real money at checkout.
The discount formula
There are two quick ways. To find the amount you save: multiply the price by the discount as a decimal — a 30% discount on $80 is 80 × 0.30 = $24 off. To find what you pay: subtract that from the price ($80 − $24 = $56), or multiply the price by (1 − discount) directly: 80 × 0.70 = $56.
The second method is fastest: for any X% off, multiply by (100 − X)/100. 25% off means × 0.75; 40% off means × 0.60. One multiplication gives you the final price.
Stacked and extra discounts
"An extra 20% off already-reduced items" doesn't add up the way it looks. The second discount applies to the already-lowered price, not the original. So 50% off then an extra 20% off isn't 70% off — it's 0.50 × 0.80 = 0.40, meaning you pay 40% of the original (a 60% total discount).
The calculator handles this correctly, but the takeaway is: stacked discounts multiply, they don't add. Always apply them one after another to the running price.
Step-by-step
Common mistakes to avoid
Pro tips
Frequently asked questions
How do I calculate a discount?
Multiply the price by the discount as a decimal for the savings, or by (1 − discount) for the final price. 20% off $50 = $50 × 0.80 = $40.
How do stacked discounts work?
They multiply, not add. 50% off then 20% off is 0.5 × 0.8 = 0.4, so you pay 40% of the original (60% off total).
How do I find the final price fast?
Multiply by (100 − X)/100. For 30% off, multiply by 0.70.
Is the calculator free?
Yes — free with no sign-up, and it runs instantly in your browser.
Does the discount include tax?
No — tax is normally added to the discounted price, so apply the discount first, then tax.
Calculating a discount is one quick multiplication: price × (100 − X)/100 gives the final price. Remember stacked discounts multiply rather than add, and tax comes after. Master that and you'll always know the real deal — free calculator in your browser.