How big is a 3 carat emerald cut diamond?

By HeyGema™ · Updated

In short

A 3 carat emerald cut diamond measures about 10.1 x 7.2 mm. It faces up 4% bigger than a round diamond of the same weight. On a size 6 finger it covers 44% of the width. For the same weight, a round diamond is 9.3 mm.

Carat to mm calculator

About 10.1 x 7.2 mm

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

3 ct emerald cut
10.1 x 7.2 mm
3 ct round
9.3 mm
Side by side
3 ct emerald cut inside 3 ct round
A 3 carat emerald cut diamond beside a 3 carat round, to the same scale.

3 carat emerald cut diamond size

A well-cut 3 carat emerald cut diamond measures about 10.1 x 7.2 mm (0.40 x 0.28 inches) at a length-to-width ratio of 1.40:1. It faces up 4% bigger than a round diamond of the same weight. It weighs 0.60 grams.

3 carat emerald cut size by length-to-width ratio

The same weight can be long and narrow or short and wide. These are 3 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.

1.30:1
Length x width: 9.7 x 7.5 mm
Width on the finger: 45% of a size 6 finger
1.40:1
Length x width: 10.1 x 7.2 mm
Width on the finger: 44% of a size 6 finger
1.50:1
Length x width: 10.5 x 7.0 mm
Width on the finger: 42% of a size 6 finger
1.60:1
Length x width: 10.8 x 6.7 mm
Width on the finger: 41% of a size 6 finger

3 carat emerald cut on a finger

7.2 mm
7.2 mm stone on a 16.5 mm finger: it covers 44% of the widthA 3 carat emerald cut diamond on a size 6 finger.
4
Finger width: 14.9 mm
Emerald cut covers: 48%
5
Finger width: 15.7 mm
Emerald cut covers: 46%
6
Finger width: 16.5 mm
Emerald cut covers: 44%
7
Finger width: 17.3 mm
Emerald cut covers: 42%
8
Finger width: 18.1 mm
Emerald cut covers: 40%
9
Finger width: 18.9 mm
Emerald cut covers: 38%

Emerald cut sizes near 3 carat

2.25 carat
Length x width: 9.2 x 6.6 mm
Round of the same weight: 8.5 mm
2.5 carat
Length x width: 9.5 x 6.8 mm
Round of the same weight: 8.8 mm
3 (this page)
Length x width: 10.1 x 7.2 mm
Round of the same weight: 9.3 mm
3.5 carat
Length x width: 10.6 x 7.6 mm
Round of the same weight: 9.8 mm
4 carat
Length x width: 11.1 x 7.9 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 emerald cut.

Round
Length x width: 9.3 mm
Against emerald cut: -4%
Oval
Length x width: 11.5 x 7.9 mm
Against emerald cut: +2%
Cushion
Length x width: 8.1 x 8.1 mm
Against emerald cut: -17%
Princess
Length x width: 7.9 x 7.9 mm
Against emerald cut: -11%
Asscher
Length x width: 7.9 x 7.9 mm
Against emerald cut: -19%
Radiant
Length x width: 9.4 x 7.2 mm
Against emerald cut: -6%
Pear
Length x width: 12.3 x 7.9 mm
Against emerald cut: -6%
Marquise
Length x width: 15.0 x 7.5 mm
Against emerald cut: +12%
Heart
Length x width: 9.4 x 9.4 mm
Against emerald cut: -20%
Trillion
Length x width: 10.1 x 10.1 mm
Against emerald cut: -17%
Baguette
Length x width: 11.5 x 5.8 mm
Against emerald cut: -6%

Questions

A 3 carat emerald cut diamond is about 10.1 x 7.2 mm at the usual 1.40:1 ratio.
Yes. Face-up, a 3 carat emerald cut is 4% bigger than a 3 carat round (9.3 mm).
There is no rule. The stone is 48% of the width of a size 4 finger and 40% of a size 8. 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