Dollars Off or Percent Off? Comparing Coupons, BOGO and 3-for-2

Dollars off versus percent off

A flat coupon saves the same amount on any purchase, while a percentage coupon saves more as the price rises. So there is a price at which they tie, and the comparison depends on which side of it you are on.

break-even price = dollars off ÷ (percent off ÷ 100)

Worked example: $15 off against 20% off. The break-even price is 15 ÷ 0.20 = $75. On a $50 item, $15 off beats 20% off ($15 versus $10). On a $120 item, 20% off wins ($24 versus $15). At exactly $75 both save $15.

You can also express the flat coupon as a percentage: $15 off a $60 item is 15 ÷ 60 = 25%. The discount calculator turns a price and a discount into the sale price and the amount saved.

Minimum-spend coupons

An offer such as $10 off a $50 purchase is worth 20% only when your cart is exactly $50. The bigger your cart, the smaller the effective discount: at $80, $10 off is 10 ÷ 80 = 12.5%.

Thresholds can also pull in the other direction. With $44 in your cart, adding a $6 item you actually want brings you to $50, and $10 off makes the total $40, which is $4 less than the $44 cart you started with. Check the return policy first, since returning an item can change whether the threshold was met.

What multi-buy deals really save

For items at the same price, the effective discount is the value of what you get free, divided by the full price of everything you take home.

When prices differ, the free or reduced item is normally the cheaper one, which lowers the saving. With a half-off second item, buying a $40 and a $30 item saves half of $30, which is $15 on a $70 total, or about 21.4% rather than 25%.

Caps and the cost of your actual basket

Percentage offers often have a ceiling, such as 25% off up to $30. The cap bites once the discount would exceed $30, which happens above 30 ÷ 0.25 = $120. Spending $200 under that offer still saves only $30, an effective 15%.

The surest way to compare offers is to price your real basket under each one. Take a $90 basket and three offers:

The percentage offer wins here, but with a $60 basket the same $15 coupon would pay $45 against $48 for 20% off. Re-run the comparison whenever the basket changes, and include shipping fees and any minimum-spend rules, which can erase a small saving or make one coupon unusable.

When a deal is not a deal

• You only need one. A multi-buy offer only saves money on items you would use. With buy one, get one half off, two items cost 1.5 times the price of one, so the deal helps only if you would have wanted the second item anyway.
• The base price differs. Compare final prices, not discount sizes. A larger discount on a higher starting price can still cost more than a smaller discount on a lower one.
• Unit prices differ. For anything sold by weight or volume, compare the price per ounce, liter or sheet across the sizes and brands on the shelf.
• Offers may not combine. Check whether two coupons apply together. If they do, stacked discounts do not simply add up.

The percent off calculator gives the price after a percentage discount, which is useful for checking the percentage side of a comparison.

These examples are for illustration and are not financial advice. Terms such as exclusions and expiry dates vary by retailer, so read the offer's conditions.