Trillion Cut

Trilliant, Trillian or Trielle

Trillion cut diamond - sample image
sample image
Shape: Trillion
Also known as: Trilliant, Trillian or Trielle
Cutting style: Modified brilliant
Facets: Between 31 - 50
L/W ratio: 1.00 - 1.10

Short description:

Trillion is a triangularly shaped cut developed in 1970s. It can come with curved or straight sides and can be very lively and fiery. Most often than not Trillions are used as a complimentary side stones, but can be quite dazzling in solitaire arrangements as well.

General size appearance:

Trillions typically look larger when viewed from the top compared to other shapes of the same weight, mainly due to shallower depth.

Trillion diamond size by carat

The following is a chart of actual Trillion cut diamond sizes (from 0.25 to 10 carats) with their corresponding face-up dimensions (length x width). This will give you an approximate idea of how big a stone of a certain weight looks or should look.
0.25 carat Trillion
4.87×4.87 mm
0.5 carat Trillion
6.14×6.14 mm
0.75 carat Trillion
7.03×7.03 mm
1 carat Trillion
7.74×7.74 mm
1.25 carat Trillion
8.33×8.33 mm
1.5 carat Trillion
8.86×8.86 mm
1.75 carat Trillion
9.32×9.32 mm
2 carat Trillion
9.75×9.75 mm
2.25 carat Trillion
10.14×10.14 mm
2.5 carat Trillion
10.5×10.5 mm
2.75 carat Trillion
10.84×10.84 mm
3 carat Trillion
11.16×11.16 mm
3.25 carat Trillion
11.46×11.46 mm
3.5 carat Trillion
11.75×11.75 mm
3.75 carat Trillion
12.02×12.02 mm
4 carat Trillion
12.28×12.28 mm
4.25 carat Trillion
12.53×12.53 mm
4.5 carat Trillion
12.77×12.77 mm
4.75 carat Trillion
13×13 mm
5 carat Trillion
13.23×13.23 mm
5.25 carat Trillion
13.45×13.45 mm
5.5 carat Trillion
13.66×13.66 mm
5.75 carat Trillion
13.86×13.86 mm
6 carat Trillion
14.06×14.06 mm
6.25 carat Trillion
14.25×14.25 mm
6.5 carat Trillion
14.44×14.44 mm
6.75 carat Trillion
14.62×14.62 mm
7 carat Trillion
14.8×14.8 mm
7.25 carat Trillion
14.97×14.97 mm
7.5 carat Trillion
15.14×15.14 mm
7.75 carat Trillion
15.31×15.31 mm
8 carat Trillion
15.47×15.47 mm
8.25 carat Trillion
15.63×15.63 mm
8.5 carat Trillion
15.79×15.79 mm
8.75 carat Trillion
15.94×15.94 mm
9 carat Trillion
16.09×16.09 mm
9.25 carat Trillion
16.24×16.24 mm
9.5 carat Trillion
16.38×16.38 mm
9.75 carat Trillion
16.53×16.53 mm
10 carat Trillion
16.67×16.67 mm
Length-to-width ratio: 1
Actual size is set for screen Change

Buying Guidelines: Trillion Cut

It's hard to judge trillion cuts solely by the numbers. Try to stay within the recommended parameter ranges defined below, avoid extremely shallow cuts, and look for symmetrical stones with equal sides.

Here is a quick guide on what to look for and what to avoid when buying Trillion cut diamond:

Look for:
  • Color: H or higher [depends on a setting]
  • Clarity: SI or better [explain]
  • Cut parameters:
    • Depth: 32% - 48%
    • Table: 50% - 70%
    • Polish/Symmetry: Good or better
    • Length-to-width ratio: 1.00 - 1.10
  • Diamonds certified by GIA or AGS [explain]
  • Eye-clean

Watch out for:
  • Inclusions visible to the naked eye
  • Extremely thin or extremely thick girdle
  • Fair or Poor symmetry
  • Strong blue fluorescence [explain]
  • Diamonds without GIA or AGS certification [explain]

Where To Buy Trillion Diamonds?

Online-only stores will always offer better prices compared to bricks & mortar stores, their main drawback, however, is that you rarely get the opportunity to visually inspect the diamond before purchasing. Luckily, this is not always the case. A few reputable online retailers (see below) are now providing actual Hi-Res photos of the diamonds they're selling, making it easy and safe to shop online. For best value, buy online.

Recommended online retailers:

Compare Trillion with another diamond

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carat vs. length* width* depth*
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Color Recommendation For Trillion Diamonds

Trillions tend to show color a bit more in the corners, so it's recommended to stay relatively high on the color scale. The choice of color also depends on a setting:

Solitaire Small side-stones Substantial side-stones
White gold/Platinum H+ G+ same as side-stones+
Yellow gold J+ I+ same as side-stones+
e.g. pave setting e.g. three-stone setting
Note: If side-stones are of any significant size (like in three-stone settings), you should at least match the color of the center stone with the color of the side stones, otherwise the center stone might look out of place (a bit "off-white").

For best value, go with the minimum recommended color for a particular type of setting. Color variations between H graded and higher colored Trillion cuts are so slight that it's almost impossible to tell the difference, especially when diamonds are mounted. The difference in price, however, can be quite considerable.

Clarity Recommendation For Trillion Diamonds

Trillion cuts are quite good at masking inclusions. SI1 or SI2 clarity or higher is recommended.

Note: You can always go lower in clarity, but it's going to get increasingly difficult to find an eye-clean Trillion below the minimum recommended SI2 grade.

For best value, go with the lowest clarity possible that is still eye-clean. If a diamond is eye-clean, then it doesn't really matter, if it's flawless or SI2. It will look the same, provided all other characteristics are the same.
About Diamond Clarity
Diamond clarity refers to the presence and visual appearance of the flaws inside a diamond (called inclusions) or on its surface (called blemishes). Clarity tells you to what degree these imperfections are present.

The amount of inclusions and blemishes is directly correlated to a diamond's value. Fewer imperfections mean higher price and vice versa.

Gemological laboratories grade diamond clarity as Flawless (FL), Internally Flawless (IF), Very Very Slightly Included (VVS1,VVS2), Very Slightly Included (VS1,VS2), Slightly Included (SI1,SI2), and Included (I1,I2,I3).

GIA and AGS Certified Diamonds

Professional and unbiased assessment of a diamond's characteristics is stated on a diamond grading report, commonly referred to as a certificate. Certificate, while not 100% reliable, is essential in determining a diamond's value.

The standard for diamond grading is pretty much set by GIA - Gemological Institute of America. They are the most reputable and consistent lab in the industry. AGS (American Gemological Society) is not far behind.

If a diamond is not certified by GIA or AGS, you can be pretty much certain that you are looking at lesser quality than indicated. This puts you in a bad position of not knowing the true diamond characteristics, which almost always results in overpaying. That is why a certificate from a well-respected grading lab is so important.

The bottom line: Make sure to always buy a diamond certified by either GIA or AGS. That's the only way of truly getting the quality you expect.

Diamonds with Blue Fluorescence

Blue fluorescence can have a positive, negative, or zero effect on a diamond. Diamonds in the lower color range (H or lower) can benefit from it, as it can make them look whiter, more colorless. On the other hand, strong fluorescence can cause a stone (especially in the higher color range D-G) to appear hazy or milky under certain light conditions. One of the biggest benefits of fluorescent diamonds is that they generally cost less.

GIA grades fluorescence as None, Faint, Medium, Strong, and Very Strong.

Faint fluorescence will have zero effect on color and overall appearance. Fluorescence of this type is not an issue and shouldn't be a purchasing factor.

Medium fluorescence will in most cases have zero to very small influence on color and overall appearance, however, colorless diamonds can sometimes exhibit negative effects and should be examined in different light conditions before purchasing.

Strong/Very Strong fluorescence requires caution. Generally, it's not a good idea to buy a colorless diamond with Strong/Very Strong fluorescence. As for lower color diamonds, even they can sometimes look hazy with strong fluorescence, so never buy a stone with this type of fluorescence without careful visual inspection.

If you're interested in fluorescent diamonds that have been carefully examined and do not display any negative effects of fluorescence, I recommend Brian Gavin's Blue Diamonds. Those are definitely top of the line and a great value.

Diamonds Without GIA or AGS Certificates

The problem with diamond grading labs other than GIA or AGS is that they are looser and more inconsistent in their grading standards. A GIA color H is an IGI color G and an EGL/HRD color F. The same goes for clarity.

While it's true that IGI, EGL, and HRD diamonds are sold at a discount, you can be certain that the same stones would cost less, if they would be certified by GIA or AGS. Why? Because they would get lower grades and thus lower price. Lower than discounted IGI, EGL, and HRD stones with higher grades.

Diamond merchants use IGI, EGL, HRD, and alike to maximize their profits. They know they can sell diamonds with inflated grades for more, even if they're sold at a substantial discounts. Some merchants also use their in-house certification, usually for the sole purpose of increasing their profits. These kinds of certificates are meaningless.
The bottom line: If you don't want to overpay and want to know exactly what kind of quality you're getting, then avoid diamonds without GIA or AGS certification.

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