How big is a 8 carat cushion cut diamond?

By HeyGema™ · Updated

In short

A 8 carat cushion cut diamond measures about 11.2 x 11.2 mm. It faces up 14% smaller than a round diamond of the same weight. On a size 6 finger it covers 68% of the width. For the same weight, a round diamond is 12.9 mm.

Carat to mm calculator

About 11.2 x 11.2 mm

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

8 ct cushion
11.2 x 11.2 mm
8 ct round
12.9 mm
Side by side
8 ct cushion inside 8 ct round
A 8 carat cushion diamond beside a 8 carat round, to the same scale.

8 carat cushion diamond size

A well-cut 8 carat cushion cut diamond measures about 11.2 x 11.2 mm (0.44 x 0.44 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 1.60 grams.

8 carat cushion size by length-to-width ratio

The same weight can be long and narrow or short and wide. These are 8 carat sizes at each ratio. A longer ratio runs the stone along the finger and makes it look slimmer. The face-up area stays almost the same.

1.00:1
Length x width: 11.2 x 11.2 mm
Width on the finger: 68% of a size 6 finger
1.10:1
Length x width: 11.7 x 10.7 mm
Width on the finger: 65% of a size 6 finger
1.20:1
Length x width: 12.3 x 10.2 mm
Width on the finger: 62% of a size 6 finger
1.30:1
Length x width: 12.8 x 9.8 mm
Width on the finger: 60% of a size 6 finger

8 carat cushion on a finger

11.2 mm
11.2 mm stone on a 16.5 mm finger: it covers 68% of the widthA 8 carat cushion diamond on a size 6 finger.
4
Finger width: 14.9 mm
Cushion covers: 75%
5
Finger width: 15.7 mm
Cushion covers: 71%
6
Finger width: 16.5 mm
Cushion covers: 68%
7
Finger width: 17.3 mm
Cushion covers: 65%
8
Finger width: 18.1 mm
Cushion covers: 62%
9
Finger width: 18.9 mm
Cushion covers: 59%

Cushion sizes near 8 carat

5 carat
Length x width: 9.6 x 9.6 mm
Round of the same weight: 11.0 mm
6 carat
Length x width: 10.2 x 10.2 mm
Round of the same weight: 11.7 mm
8 (this page)
Length x width: 11.2 x 11.2 mm
Round of the same weight: 12.9 mm
10 carat
Length x width: 12.1 x 12.1 mm
Round of the same weight: 13.9 mm

8 carat in other shapes

Every row is a well-cut diamond of 8 carat. The last column is the face-up size against the cushion.

Round
Length x width: 12.9 mm
Against cushion: +16%
Oval
Length x width: 16.0 x 11.0 mm
Against cushion: +23%
Princess
Length x width: 11.0 x 11.0 mm
Against cushion: +7%
Emerald cut
Length x width: 14.0 x 10.0 mm
Against cushion: +21%
Asscher
Length x width: 11.0 x 11.0 mm
Against cushion: -2%
Radiant
Length x width: 13.0 x 10.0 mm
Against cushion: +14%
Pear
Length x width: 17.0 x 11.0 mm
Against cushion: +13%
Marquise
Length x width: 20.8 x 10.4 mm
Against cushion: +35%
Heart
Length x width: 13.0 x 13.0 mm
Against cushion: -4%
Trillion
Length x width: 14.0 x 14.0 mm
Against cushion: +1%
Baguette
Length x width: 16.0 x 8.0 mm
Against cushion: +14%

Questions

A 8 carat cushion cut diamond is about 11.2 x 11.2 mm at the usual 1.00:1 ratio.
No. Face-up, a 8 carat cushion is 14% smaller than a 8 carat round (12.9 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