Discount Calculator
Calculate the sale price after a percentage discount, including optional sales tax.
The price before the discount.
The percentage off the original price.
Optional sales tax applied after the discount.
How to Calculate a Discount
Calculating a discount is straightforward: multiply the original price by the discount percentage, then subtract from the original price.
Formula: Sale Price = Original Price × (1 - Discount% / 100)
For example, a $80 item at 25% off: $80 × 0.75 = $60. You save $20.
If sales tax applies, it's calculated on the discounted price, not the original. So if tax is 8%: $60 × 1.08 = $64.80.
Stacking Discounts
When multiple discounts apply (like 20% off + an extra 10% off), they don't simply add up to 30%. Instead, each discount applies to the already-reduced price:
- $100 at 20% off = $80
- $80 at an extra 10% off = $72
The combined effect is 28% off, not 30%. This is why retailers can advertise "extra" discounts that sound better than they are.
When Is a Sale Actually a Good Deal?
Not all discounts represent genuine savings. Here are some tips:
- Compare per-unit prices: A "buy 2 get 1 free" deal is effectively 33% off, which may or may not beat a flat 25% discount depending on how many you need.
- Check price history: Some retailers inflate prices before sales to make discounts look larger.
- Consider the cost per use: A $200 jacket at 50% off ($100) that you wear 100 times costs $1/wear — better value than a $20 shirt worn twice ($10/wear).
- Don't buy just because it's on sale: A 50% discount on something you don't need still costs money.
Frequently Asked Questions
How do I calculate a percentage off in my head?
Is sales tax calculated before or after the discount?
What does "up to 50% off" mean?
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