"The typical cash-back return rate is 1 percent," says Anuj Shahani, director of competitive tracking services at Synovate.

However, some cash-back cards give you the opportunity to boost your payout based on spending level, purchases made in certain spending categories or category bonuses. For instance, the Chase Freedom card and Discover More offer 5 percent cash-back in certain purchase categories that change. Blue Cash from American Express offers 5 percent cash back on "everyday purchases" once you hit a spending threshold of $6,500.

Bankrate.com's cash-back credit cards study makes it easy to compare cards. Our chart shows the "cash-back ratio," which lists the rate or rates of return offered on transactions, and the "reward formula," which details the reward offering and explains the break points for higher payouts.

Of the 32 cards surveyed, 28 percent offered higher returns for purchases made in certain spending categories. Nineteen percent of the cards offered tiered reward rates based on spending level.