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Discount Calculator

Calculate sale prices, savings, and discounts. Find the final price after percent off, or reverse-calculate the original price.

Discount Worksheet
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Discount Calculation Modes

This calculator supports four different discount scenarios:

1. Percent Off

Calculate the sale price when you know the original price and discount percentage.

Formula: Final = Original × (1 - Discount%/100)

Example: $150 at 30% off = $150 × 0.70 = $105

2. Dollar Amount Off

Calculate the sale price with a fixed dollar discount.

Formula: Final = Original - Discount Amount

Example: $80 with $15 off = $65

3. Find Original Price

Calculate the original price from a sale price and discount percentage.

Formula: Original = Final / (1 - Discount%/100)

Example: $42 after 30% off → $42 / 0.70 = $60

4. Find Discount Percentage

Calculate what percent off a sale represents.

Formula: Discount% = ((Original - Final) / Original) × 100

Example: $200 → $150 = ((200-150) / 200) × 100 = 25% off

Shopping Tips

  • Compare unit prices: A smaller discount on a cheaper item may still be the better deal
  • Watch for stacked discounts: "Extra 20% off sale prices" means 20% off the already-reduced price
  • Consider total value: Free shipping on higher minimum vs. a percentage discount
  • Time your purchases: End-of-season sales often offer the deepest discounts

How Stacked Discounts Work

Multiple discounts are applied sequentially, not added together. This is a common source of confusion:

  • 20% + 10% off $100: $100 × 0.80 = $80 → $80 × 0.90 = $72 (not $70)
  • 30% + 20% off $100: $100 × 0.70 = $70 → $70 × 0.80 = $56 (not $50)
  • Order doesn't matter: 20% then 10% gives the same result as 10% then 20%

Two stacked discounts always save less than their sum. A "50% + 50% off" sale results in 75% off — not free.

BOGO and Bulk Deals

  • Buy one, get one free (BOGO): Effectively 50% off when buying 2 items
  • Buy one, get one 50% off: Only 25% off per item (on 2 items)
  • Buy 2, get 1 free: 33% off per item (on 3 items)

BOGO deals are only worth it if you actually need the extra quantity. Compare the per-unit cost to other sizes or brands before committing.

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Frequently Asked Questions

How much is 20% off $100?

20% off $100 is $80, a saving of $20. The rule is final price = original price x (1 minus the discount as a decimal), so $100 x 0.80 = $80. A quick mental shortcut for 15% off: take 10% by moving the decimal one place, add half of it, so 15% off $80 saves $12 and costs $68.

How do I find the original price before a discount?

Divide the sale price by (1 minus the discount as a decimal). An item that costs $80 after 20% off had an original price of $80 / 0.80 = $100. The reverse also works for checking the advertised percentage: discount = (original minus final) / original x 100, so $100 reduced to $75 is a 25% discount.

Is 20% off then 10% off the same as 30% off?

No. Stacked percentage discounts multiply rather than add. 20% off and then 10% off $100 gives $100 x 0.80 x 0.90 = $72, a 28% total discount, while a single 30% off gives $70. The order of the two discounts does not change the result, but a fixed dollar coupon does depend on when it is applied.

Does sales tax apply before or after a discount?

In most places sales tax is charged on the price after the discount. A 20% discount on a $100 item leaves an $80 taxable amount, so tax is calculated on $80, not $100. Manufacturer coupons can be an exception in some US states, where tax is charged on the price before the coupon.