Mathematical Formula & Method
Discount Calculator Formula
Discount Amount = Original Price × (Discount % / 100) | Final Price = Original Price − Discount + Tax
The Discount Calculator helps shoppers and retailers compute the final price after a percentage discount or dollar reduction, with optional sales tax applied to the discounted total.
Worked Examples & Step-by-Step Solutions
$120 item with 25% discount
- Calculate discount amount: $120 × 0.25 = $30.00.
- Subtract discount from original: $120 − $30 = $90.00.
- Savings: You save $30.00.
$250 item with 40% discount and 8% sales tax
- Discount: $250 × 0.40 = $100.00.
- Discounted price: $250 − $100 = $150.00.
- Tax (8% on $150): $150 × 0.08 = $12.00.
- Total final price: $150 + $12 = $162.00.
How to Use the Discount Calculator
- Enter the original retail price before discounts.
- Enter the discount percentage (e.g. 20 for 20% off).
- Optionally add local sales tax percentage.
- Click Calculate to see how much you save and what you pay.
Important Assumptions & Unit Conventions
- Discounts cannot exceed 100% in conventional retail sales.
Frequently Asked Questions
How do you calculate 20% off?
Multiply the price by 0.20 to find the discount, then subtract it. Or directly multiply the original price by 0.80.
What is 30% off $50?
Discount = $50 × 0.30 = $15. Final price = $50 − $15 = $35.
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