IGS may receive customer referral fees from the companies listed in this page. Learn more.

Buying a Trillion-Cut Diamond

Save Money on Your Jewelry With These Sales and Coupons * See website for exclusions and restrictions.
If you’re looking for a diamond that will stand out from the crowd, a trillion shape could be a great option for you. Also called trilliant or triangle diamonds, these stones have a large face-up size and attractive prices. However, there’s a catch. Finding one can be very difficult, let alone a good-quality center stone. Learn whether this shape is right for your ring and how to judge a trillion-cut diamond.
By Addison Rice 5 minute read
Find this Ring at CustomMadeA trillion-cut diamond adds a distinctive geometry to any ring. © CustomMade. Used with permission.

Working with a custom jeweler like CustomMade will help you find the perfect trillion to feature in your ring. Plus, the ring will be custom-fit to your diamond, so there’s no headaches when setting the stone.

The Pros and Cons of a Trillion-Cut Diamond

Every diamond shape has its benefits and drawbacks. Ultimately, you should get the diamond shape that works best for your style.

Pros: Size, Cost, and Style

There are plenty of good reasons to get a trillion-cut diamond. Did you know that a trillion-cut diamond will look larger than a round with the same carat weight? In fact, it doesn’t just look larger, it actually has a surface about 12% bigger. A trillion has the largest face-up area of any diamond shape, except a marquise.

0.34ct trillion
At 0.34 cts, this center stone has a face-up size comparable to that of a 0.5-ct round. Photo courtesy of Apple Tree Auction Center and liveauctioneers.com.

A trillion will also cost much less than a round of the same weight. Round diamonds sell at a premium due to high demand. So, choosing any fancy shape — any finished shape other than round — can save you some money.

Finally, you’ll rarely see trillions as center stones, so your ring is sure to be an eye-catcher. If you have eclectic tastes, there’s no better reason to buy a trillion-cut diamond. The sharp points and steep angles also make this shape a great option for a modern look.

trillion style
Trillion-cut diamonds make a bold statement. Photo courtesy of Freeman’s and liveauctioneers.com.

Cons: Fragile Corners, Hard to Find

The trillion does have some physical weaknesses. Although diamonds are famously resistant to scratching, the sharp corners of a trillion-cut diamond are likely to chip and break. Make sure to have the stone placed in a protective setting, such as V-shaped prongs or a bezel.

bezel set trillion engagement ring
Although prongs will protect the diamond well enough, a bezel setting provides more security (and won’t snag on clothing). Photo courtesy of Ewbank’s and liveauctioneers.com.

Perhaps the most significant drawback to choosing a trillion is limited availability. Major retailers like James Allen or Blue Nile don’t carry trillion-cut diamonds. Instead, try working with a custom jeweler like CustomMade. They can source the perfect trillion-cut diamond for your ring.

Judging Trillion Quality

Unlike round diamonds, trillions don’t have any specific guidelines for good cut quality. Instead, you’ll just have to shop around for a trillion that looks good. If you’re buying online, that means you’ll have to find a vendor that provides good pictures and videos of your diamond. If you’re shopping at a brick-and-mortar store, make sure the merchant shows you your diamond from all angles.


Limit your search to certain proportions. Make sure the total depth percentage is between 32 and 48% to prevent light leakage. Limit the table width to 50 to 70% of the diamond width, too. Finally, you’ll want a length-to-width ratio of 1.0 to 1.1 to avoid an off-shape trillion.

odd proportions
This trillion has a very odd shape. Photo courtesy of DuMouchelles and liveauctioneers.com.

Shape Appeal

Symmetry is essential to shape appeal, but it’s not the only important aspect. You should consider the type of trillion shape you want for your ring.

Flat or Rounded Sides?

Do you want flat sides or rounded sides? Flat sides will give your ring a strong geometric look, while rounded trillions are generally preferred for a diamond center stone. Rounding can also be slight or prominent, whatever fits your style.

shape appeal
With great proportions and rounded edges, this center stone has amazing shape appeal. Photo courtesy of 21st Century Auctions and liveauctioneers.com.
Sharp Corners?

Consider the type of corners you’d prefer, too. Most trillions have sharp corners that are susceptible to damage. On the other hand, some have cut-off corners that are less likely to break. However, these will give the diamond a different look.

sharp geometry
The sharp corners in this trillion-cut diamond pair with princess-cut side stones for a dramatically geometric look. Photo courtesy of Wickliff & Associates Auctioneers and liveauctioneers.com.
Look for Symmetry

Next, look for symmetry. Trillions should be equilateral triangles, so all three angles should be equal and all three sides should have the same length.

uneven sides
The sides of this trillion-cut diamond appear to have unequal lengths. Photo courtesy of Alex Cooper and liveauctioneers.com.

The back facets should provide light return in a symmetrical fashion, too. If one area is more sparkly than another, this indicates poor cut quality.

Rounded sides should be equally round and without bulges.

Clarity for a Trillion Diamond

Since trillions are a brilliant cut, they should hide inclusions well. An SI clarity trillion will very likely appear eye-clean when set in a ring.

si2 clarity trillion-cut diamond
Just because this diamond has an SI2 clarity doesn’t mean it looks bad. Photo courtesy of 1 Great Deal Auctions and liveauctioneers.com.

That said, since a well-cut trillion is so hard to find, we recommend keeping your search as open as possible. Consider every clarity grade from SI2 and up, so you can find a diamond with good shape appeal and top sparkle.

Color in a Trillion Diamond

Like clarity, color is a secondary concern. Ultimately, you just want the diamond to look white in your ring. Jewelry metals can have a major effect on what a diamond’s color looks like in its setting. So, for white gold and platinum settings, stick to a diamond color grade of H or better. In yellow gold or rose gold settings, a color grade of J or better will look beautiful.

j color trilliant diamond
J color can still look good in white gold. Photo courtesy of Jasper52 and liveauctioneers.com.

Where Can I Buy a Trillion-Cut Diamond?

Since most retailers don’t carry trillion-cut diamonds, it’s best to work with a custom jeweler. CustomMade is an online jeweler that creates jewelry tailored to your style and budget. Their experience can point you towards a great trillion diamond.

trillion-cut diamond and emerald engagement ring
Find this Ring at CustomMadeA custom jeweler will do the hard work of sourcing your diamond. © CustomMade. Used with permission.