How big is a 3 carat trillion cut diamond?

By HeyGema™ · Updated

In short

A 3 carat trillion cut diamond measures about 10.1 x 10.1 mm. It faces up 14% smaller than a round diamond of the same weight. On a size 6 finger it covers 61% of the width. For the same weight, a round diamond is 9.3 mm.

Carat to mm calculator

About 10.1 x 10.1 mm

An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.

3 ct trillion
10.1 x 10.1 mm
3 ct round
9.3 mm
Side by side
3 ct round inside 3 ct trillion
A 3 carat trillion diamond beside a 3 carat round, to the same scale.

3 carat trillion diamond size

A well-cut 3 carat trillion cut diamond measures about 10.1 x 10.1 mm (0.40 x 0.40 inches) at a length-to-width ratio of 1.00:1. It faces up 14% smaller than a round diamond of the same weight. It weighs 0.60 grams.

3 carat trillion on a finger

10.1 mm
10.1 mm stone on a 16.5 mm finger: it covers 61% of the widthA 3 carat trillion diamond on a size 6 finger.
4
Finger width: 14.9 mm
Trillion covers: 68%
5
Finger width: 15.7 mm
Trillion covers: 64%
6
Finger width: 16.5 mm
Trillion covers: 61%
7
Finger width: 17.3 mm
Trillion covers: 58%
8
Finger width: 18.1 mm
Trillion covers: 56%
9
Finger width: 18.9 mm
Trillion covers: 53%

Trillion sizes near 3 carat

2.25 carat
Length x width: 9.2 x 9.2 mm
Round of the same weight: 8.5 mm
2.5 carat
Length x width: 9.5 x 9.5 mm
Round of the same weight: 8.8 mm
3 (this page)
Length x width: 10.1 x 10.1 mm
Round of the same weight: 9.3 mm
3.5 carat
Length x width: 10.6 x 10.6 mm
Round of the same weight: 9.8 mm
4 carat
Length x width: 11.1 x 11.1 mm
Round of the same weight: 10.2 mm

3 carat in other shapes

Every row is a well-cut diamond of 3 carat. The last column is the face-up size against the trillion.

Round
Length x width: 9.3 mm
Against trillion: +16%
Oval
Length x width: 11.5 x 7.9 mm
Against trillion: +22%
Cushion
Length x width: 8.1 x 8.1 mm
Against trillion: -1%
Princess
Length x width: 7.9 x 7.9 mm
Against trillion: +6%
Emerald cut
Length x width: 10.1 x 7.2 mm
Against trillion: +20%
Asscher
Length x width: 7.9 x 7.9 mm
Against trillion: -2%
Radiant
Length x width: 9.4 x 7.2 mm
Against trillion: +13%
Pear
Length x width: 12.3 x 7.9 mm
Against trillion: +12%
Marquise
Length x width: 15.0 x 7.5 mm
Against trillion: +34%
Heart
Length x width: 9.4 x 9.4 mm
Against trillion: -4%
Baguette
Length x width: 11.5 x 5.8 mm
Against trillion: +13%

Questions

A 3 carat trillion cut diamond is about 10.1 x 10.1 mm at the usual 1.00:1 ratio.
No. Face-up, a 3 carat trillion is 14% smaller than a 3 carat round (9.3 mm).
There is no rule. The stone is wider than most fingers. Compare it with a ring you have tried on in the finger chart above.
Yes. A lab grown diamond has the same density as a mined one, so it measures the same for the same weight.

More size charts