Bargain-hunting sites don't typically feature half-off coupons for engagement rings, but you can still get a great deal if you understand how diamonds are priced. While you can always save money by purchasing a lower-grade diamond, there are other ways to reduce how much a diamond ring costs without sacrificing quality. Here's how you can score a deal on a diamond engagement ring without waiting for a sale, regardless of whether you shop at a national chain, local jeweler or online.

Choose a Smaller Stone

A smaller diamond, of course, costs less than a larger one (assuming all the other factors, such as clarity, color and cut are equal). When purchasing a smaller diamond, though, you'll pay less per carat than if you spring for a larger one.

As Lumera Diamonds explains, less than 1 in 1,000,000 rough diamonds are big enough to cut a 1-carat diamond from. Because larger rough diamonds are rare, they cost more on a per-carat basis than smaller ones. According to Lumera Diamond, you might expect to pay:

• $6,000 per carat for a 1-carat diamond (for a total of $6,000)
• $12,000 per carat for a 2-carat diamond (for a total of $24,000)
• $18,000 per carat for a 3-carat diamond (for a total of $54,000)

Go Just Under the Popular Size

Popular sizes for diamonds include round numbers and half-carats. For instance, 1-, 1.5- and 2-carat diamonds are all common favorites. Diamonds that are just under these sizes, say 1.9 carats instead of a full 2 carats, don't command quite as high a per-carat price because jewelers can't advertise them as the next-popular size.

By selecting a diamond that's just below a popular size, you'll be able to save money without sacrificing too much size. According to DailyFinance, you could save 20 percent by just dropping from a 1-carat diamond to one that's 0.95-carats. The difference in price comes at virtually no sacrifice in beauty, because .05 carats is only 10 milligrams. It's so small that no one will notice.

Opt for a Marquise Cut

If you're going for a smaller diamond, the marquise cut can make it look larger than it actually is. This cut has a large crown that showcases much of the actual diamond. There are few carats hidden below the crown. The cutss 56 facets, Diamond Registry notes, makes the stone sparkle, maximizing its beauty.

Select a Shallow Setting

How the ring displays the diamond significantly affects how large or small the stone appears. A shallow setting will prominently display the diamond. If you're using a marquise cut, look for a shallow setting that has at least four prongs. Should one of the prongs break, the other three will keep the diamond secure until you can get the ring repaired by a professional jeweler.

Look for a Thin Band

You may also want to look for a thin band, as this will also maximize the diamond's appearance. A thin band will create an optical illusion and make the diamond look bigger than it really is. Conversely, a thicker band would make the diamond appear smaller -- an effect you don't want in your engagement ring. Of course, the band should be thick enough to securely support the diamond, but staying with the minimum thickness that's safe will keep your marquise diamond looking big.

When it comes time to propose, you don't need to wait for a great sale on diamond engagement rings. Understand how diamonds are priced, and look for a smaller one that's just below a popular size. You should be able to get a great price on the stone, and you can make it look bigger than it actually is by selecting a marquise cut, shallow setting and narrow band.