SHOPPING MATH GUIDE
20% Extra vs. 20% Off
See why 20% more product is not the same as 20% off, with a simple unit-price comparison.
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Everyday math,
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Quick, practical calculators for comparing deals at the store or online.
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Extra vs. Discount
Is 20% more product better than 20% off? Compare both offers by unit price.
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3 calculators available in English.
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Shopping & Money
Compare promotions, unit prices, and package-size changes.
- Extra vs. DiscountCompare a bonus-size offer with a percentage discount to see which one gives you a lower unit price.Open calculator
- Buy X, Get Y FreeConvert a buy-X-get-Y-free deal into an effective discount, total cost, and price per item.Open calculator
- ShrinkflationCompare price and package-size changes to find the effective change in unit price.Open calculator
GUIDES
The math behind common store promotions
SHOPPING MATH GUIDE
Buy 3, Get 1 Free: Percent Off
Learn why buying three items and getting one free works out to an effective 25% discount.
SHOPPING MATH GUIDE
How to Calculate Shrinkflation
Use unit prices to measure the real price increase when a package gets smaller, more expensive, or both.
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