Trillion Cut Diamond: Pros, Cons & Spread

Bowed sides make the trillion rounder in the hand than the straight-sided trilliant, though both are three-sided brilliants. Ours is a shallow stone: 50.7% deep, with a 56.6% table, a 36.0° crown, a 31.91° pavilion and 73 facets.

Against the T73 Round Brilliant it has two pros and three cons. It is a popular solitaire shape for coloured stones as well as a side stone. In diamond, the numbers say what that shape costs and what it gives.

Is a trillion a good cut for diamond? Pros and cons

Cons

Much less light than a round 67 vs 93
Much more light leaks 13 vs 2
A little less light when tipped 87 vs 92

Compared with the T73 Round Brilliant in diamond. A difference counts from 3 points (Brilliance, Fire, Tilt, Leakage), 5 (Scintillation, Symmetry), 2 (Spread) or 5% (weight); Tilt counts as a pro only for a stone within 5 points of the brilliance it is compared with. How we measure.

All eight scores against the T73

At a glance: the Trillion Cut in diamond (white) against the T73 Round Brilliant in diamond (dashed): solid white where it reaches further, hatched where it falls short. Each pro and con is explained, with pictures, below.

Against the T73 Round Brilliant in diamond: ahead on 2, level on 2, behind on 4.

Global81, the comparison 90, difference −9
Brilliance67, the comparison 93, difference −26
Fire87, the comparison 78, difference +9
Scintillation80, the comparison 80, difference 0
Spread107, the comparison 100, difference +7
Symmetry100, the comparison 100, difference 0
Shape-norm78, the comparison 100, difference −22
Tilt87, the comparison 92, difference −5

Face-up light census, a different measure from the Cut Grading Tool; Spread and Shape-norm above 100 sit on the ring.

Open it in the Cut Performance Wheel

What diamond gains in a trillion

More fire than the T73

Fire 87 against 78 for the T73 Round Brilliant in diamond: 9 points higher

Fire is clearly ahead of the benchmark. A broad table over a shallow pavilion sends returning light out at low angles, where diamond's dispersion of 0.044 has room to spread it into colour.

Trillion cut in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 87) — Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

T73 round brilliant in diamond face-up under a single bright light: a render from our simulator, its coloured flashes are the fire (score 78) — Look at the coloured flashes: those are fire. Same light, same size, same face-up angle; rendered by our 3D Gemstone Simulator from each cut's own model.

Try it yourself: See the fire in the 3D Gemstone Simulator

A larger face for its weight

Spread 107 against 100 for the T73 Round Brilliant in diamond: 7 points higher

At 50.7% deep, little of the stone sits below the girdle, so a trillion of a given carat weight shows more face than a T73. Only two cuts we measure in diamond have a larger face for their weight.

Trillion Cut · 7.01 mm at 1.00 ct · Spread 107

T73 Round Brilliant · 6.48 mm at 1.00 ct · Spread 100

Both stones weigh 1.00 ct in diamond and are drawn to the same scale, from each cut's own model. Spread is face-up size per carat: a deeper stone carries more weight below the girdle and looks smaller for its weight.

Try it yourself: Compare the Spread spoke in the Cut Performance Wheel

The trillion's costs in diamond

Much less light than a round

Brilliance 67 against 93 for the T73 Round Brilliant in diamond: 26 points lower

Brilliance trails by a wide margin. The pavilion figure, 31.91°, is well under the 38.9° guide minimum we use for round designs, and in a shallow stone more of the light passes out through the back.

Trillion cut in diamond face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 67) — Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

T73 round brilliant in diamond face-up Light Return map: red, green and blue show where the light returns from, grey shows where it leaks (Brilliance 93) — Red, green and blue = light returning to the eye; grey = light leaving through the pavilion. This is the head-on view; the Brilliance score averages a wider cone of light, so the score can differ from what one picture shows.

What helps: The Trilliant Cut Diamond keeps three sides and returns 78. We have not measured a deeper trillion, so we cannot promise what steeper angles would give.

Try it yourself: Open this Light Return map in the simulator

Much more light leaks

Leakage 13 against 2 for the T73 Round Brilliant in diamond: 11 points higher

Our census lets 13% of the trillion's light out of the back, set against 2% for the T73. It is the cost of the shallow profile that gives the trillion its spread.

Trillion cut in diamond tilted 0 degrees: Light Return map, 16% of the face leaking — Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

Trillion cut in diamond tilted 10 degrees: Light Return map, 17% of the face leaking — Each frame is the Light Return map with the stone tilted away from you by the angle shown; grey is light leaving through the pavilion. The share under each frame is that picture's own.

What helps: A smaller stone leaks the same share. The Trilliant Cut Diamond loses 11%; for far less, a round such as the T73 Round Brilliant Diamond.

Try it yourself: Tilt it yourself in the simulator's light map

A little less light when tipped

Tilt 87 against 92 for the T73 Round Brilliant in diamond: 5 points lower

Tipped by 20°, it keeps 87 of its face-up light, against 92: a small gap next to its light and leakage.

Try it yourself: Compare the Tilt spoke in the Cut Performance Wheel

Who a trillion diamond suits

Choose the trillion when face size and colour matter more than light: it shows more face for its weight than almost anything we measure and has more fire than the T73. It suits a solitaire or side stone where a soft triangle is wanted.

For more light in three sides, the Trilliant Cut Diamond; for the most light, a round. If you want spread and fire with a square outline, the Emerald Square Cut Diamond scores 108 for spread and 84 for fire.

Trillion Cut Diamond: questions

Does a trillion cut diamond look big for its weight?

Yes: Spread 107 against 100 for the T73, so a trillion shows more face at the same carat weight.

Is a trillion cut diamond brilliant?

Less than a round: Brilliance 67 against 93, with 13% of the light leaking.

Trillion or trilliant cut diamond?

The trillion has more fire (87 against 83) and spread; the trilliant returns more light (78 against 67).

What does a 6.5 mm trillion diamond weigh?

Just 0.80 ct, light for its width because the model is so shallow.

Get the Trillion Cut files

6 formatsMillimetresWatertight

Trillion Cut 3D files

The Trillion Cut as exact geometry: 73 planar facets, real-world scale, ready for CAD, rendering, printing and casting.

STEPExact faceted solid for CAD
3DMRhino, closed mesh on its own layer
STLWatertight mesh for printing and casting
OBJMesh for modelling and rendering
FBXBlender, 3ds Max, Maya, Cinema 4D, Unity, Unreal
GLBWeb, AR and quick previews

€9.99 · Personal useBuy the 3D files

GemCad120 index

Trillion Cut cutting files

The Trillion Cut as a faceting design: 61 + 12 girdles = 73 facets, 120 index, 3-fold symmetry, ready for the machine.

.ascGemCad design file, 120 index gear
.csvTier table: angles, indices and cutting order
DiagramPrintable faceting diagram

€9.99 · Personal useBuy the cutting files

Questions before you buy? Email us.

More gemstones and cuts

Diamond: optical properties and the top ten cuts · The Trillion Cut: specifications, model and files

Trillion Cut Diamond: more fire and a larger face for its weight