There’s a hard and fast rule about couponing, which differentiates a tightwad from a cheapskate. Truly frugal purchases (by tightwads) are made of only the needed items.

For example—I keep coupons for stores that work on any product. My 20% off at Office Depot recently made a purchase of paper competitive to my regular supplier when they were out.

But a coupon for brand-name diapers is only “good” if it reduces the price of the diapers more than the price of a comparable store brand. I have a few coupons in my coupon box for deodorant. We don’t have a huge brand-loyalty to that particular item, so when we price-compare, we’ll just deduct the thirty cents from that brand before we compare with the others on the shelf.

Coupons only save you money if you’re buying an item you were already going to buy, and if there isn’t a better deal without a coupon.

This post is part of a series I’ve entitled “Frugal August” and is inspired by (though not copied from) the book The Complete Tightwad Gazetteby Amy Dacyczyn. My tips are meant to build on hers, but generally are not duplications.