How Do You Calculate a Discount?

The Discount Formula

The math behind any percent-off deal comes down to one formula:

• Final price = original price × (1 − p/100)
• Savings = original price × (p/100)

So if something costs $80 and is 25% off, the final price is 80 × 0.75 = $60, and you save $20. If that same item were 30% off: 80 × 0.70 = $56, saving $24. The formula scales to any price or percentage without a separate calculator.

The single most common mistake is subtracting the percentage as if it were a dollar amount — taking $25 off an $80 item for a 25% discount, which would give $55 instead of the correct $60. Percent off is always a fraction of the price, not a flat figure, so the bigger the price, the bigger the dollar saving for the same percentage. That is why 25% off a $200 jacket saves $50, while 25% off a $20 shirt saves only $5, even though the sticker says the same number.

Worked Examples

Here are three quick examples using the formula:

• 25% off $80: 80 × 0.75 = $60 (save $20)
• 30% off $50: 50 × 0.70 = $35 (save $15)
• 40% off $120: 120 × 0.60 = $72 (save $48)

Notice the pattern: the multiplier is always 1 minus the decimal form of the discount. 20% off → multiply by 0.80; 15% off → multiply by 0.85. Once that clicks, you can run estimates in your head for any tag you see.

Mental-Math Shortcuts

You don't always need the full formula. These shortcuts let you sanity-check a deal in seconds:

• 10% off: move the decimal one place left. 10% of $47 = $4.70.
• 30% off: find 10%, then multiply by 3. 10% of $50 = $5; × 3 = $15 off → $35.
• 5% off: find 10%, then halve it. 10% of $60 = $6; half = $3 off → $57.
• 25% off: divide by 4. $80 ÷ 4 = $20 off → $60.
• 50% off: divide by 2. $90 ÷ 2 = $45.

These shortcuts are especially handy in a busy store when you just need a quick gut-check before reaching for your phone.

Use the App for Instant Results

When the mental math feels like too much — or you want a verified number before checkout — Discount Calculator: % Off gives you the final price, the amount saved, and the percent off all on one screen in under 3 seconds. You can type the price or point your camera at a store price tag and let the app read it for you. No mis-keyed digits, no second-guessing. The result is immediate, and every calculation is saved automatically to your private History tab so you can compare prices across a shopping trip.