A store advertises 20% off and lets you apply another 10% discount. It is tempting to read that as 30% off. When the second discount applies to the already-reduced price, however, you save 28% overall. The difference becomes easier to see if you calculate each step rather than combining the headline numbers.

The examples here are hypothetical arithmetic, not offers from a retailer. Whether discounts can be combined, which items qualify, and how shipping and taxes are calculated depend on the actual terms and checkout.

Follow the remaining price

Take a jacket priced at $100. A 20% reduction removes $20, leaving $80. Applying 10% to that $80 removes another $8. The jacket now costs $72 before any applicable shipping or tax. The total reduction is $28, not $30.

For successive percentage discounts on the same eligible amount, multiply the price by the proportion left after each discount. In this example, $100 × 0.80 × 0.90 = $72. Reversing those two percentages gives the same result before rounding, provided they apply to exactly the same items and no threshold changes their eligibility.

Fixed-dollar offers make the order matter

Now compare $10 off followed by 20% off with 20% off followed by $10 off. Starting at $100, the first arrangement leaves $90 and then $72. The second leaves $80 and then $70. You cannot assume the more favorable order is available; the merchant decides how its promotions apply.

A minimum-purchase condition can create another difference. If an offer requires a qualifying subtotal of $100, an earlier reduction might move the order below that threshold. Read whether the minimum is calculated before or after other discounts and whether excluded items contribute to it.

A cart is not always one eligible amount

Imagine a $60 shirt and a $40 accessory. If a 20% code applies only to the shirt, it saves $12, not $20. The combined merchandise subtotal becomes $88. A second cart-wide offer may still exclude the accessory, apply only to full-price items, or fail to combine at all.

This is why the promotion's exclusions matter more than a shortcut formula. Check the individual line prices after entering a code. If the checkout shows only a total reduction, compare the result with the qualifying items and read any notice explaining a rejected or replaced promotion.

Compare the amount you will actually pay

A lower merchandise subtotal can lose free shipping. For example, reducing an $80 cart to $72 does not save the full $8 if it also introduces a shipping charge. Compare the final payable totals for the same delivery method and destination. Do not add an unwanted product merely to make a threshold look attractive.

Keep a note or screenshot of the promotion terms with your order confirmation if the offer is important to the decision. If the result is unclear, ask the retailer before paying. An apparently bigger stack is not automatically a better purchase than one straightforward discount with clear return terms and an item you already intended to buy.