What does 'buy one get one 50% off' really save?

BOGO 50% is a 25% discount across two items: you pay full price for one and half for the other, so 1.5 items' price for 2 items = 75% of the total, a 25% saving.

Discount Calculator

Q: How do I calculate a discount?

Multiply the price by the discount percentage to get the savings, then subtract. A $80 item at 25% off saves 80 × 0.25 = $20, for a $60 sale price.

Q: How do stacked discounts work?

Two discounts apply one after the other, not added together. 20% off then an extra 10% off is not 30% off — it's 0.80 × 0.90 = 0.72, so 28% off. A $100 item becomes $72, not $70.

Find the sale price and what you save — including the real math behind stacked "extra % off" deals.

Final price

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You save

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Effective discount

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Price after discount

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Tax added

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The discount formula

Sale price = Price × (1 − discount)
Stacked: Price × (1 − d1) × (1 − d2) (not 1 − d1 − d2)

Worked example

$80 at 25% off: saves $20 → $60.

Stack an extra 10%: 80 × 0.75 × 0.90 = $54, an effective 32.5% off — not 35%.

Deal math worth knowing

Retail promotions are designed to sound bigger than they are. "20% off plus an extra 10%" is 28% off, not 30%. "Buy one get one 50% off" is only 25% off the pair. And a percentage off a marked-up price can still be more than a competitor's everyday price — always compare the final number, not the discount size. Enter a tax rate above to see the true out-the-door price, and use the percentage change calculator to compare two final prices directly.

Frequently asked questions

How do I calculate a discount?

Price × discount % = savings; subtract from price. $80 at 25% off saves $20 → $60.

How do stacked discounts work?

They multiply, not add. 20% then 10% = 0.8 × 0.9 = 28% off, not 30%.

What does BOGO 50% really save?

25% across the two items.

Related calculators

Note: Educational tool; store promotions may have exclusions. Last reviewed: July 2026.