How big is a 4 carat opal?
By HeyGema™ · Updated
In short
A 4 carat round opal measures about 12.2 mm across (0.48 inches), 19% wider than a 4 carat diamond (10.2 mm). An oval of the same weight is 15.1 x 10.4 mm and an emerald cut 13.2 x 9.4 mm.
- 12.2 mmround opal, across
- 0.48 inthe same in inches
- 0.80 gweight
- 74%of a size 6 finger's width
Carat to mm calculator
About 12.2 x 12.2 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
Round
12.2 mm
Oval
15.1 x 10.4 mm
Cushion
10.6 x 10.6 mm
Princess
10.4 x 10.4 mm
Emerald cut
13.2 x 9.4 mm
Asscher
10.4 x 10.4 mm
Radiant
12.3 x 9.4 mm
Pear
16.0 x 10.4 mm
Marquise
19.6 x 9.8 mm
Heart
12.3 x 12.3 mm
Trillion
13.2 x 13.2 mm
Baguette
15.1 x 7.5 mm
= 5 mm in every picture above
4 carat opal size by shape
Face-up measurements of a well-cut 4 carat opal. Opal is lighter than diamond (2.10 against 3.52), so the same weight gives a bigger stone, 19% wider across.
- Round
- Length x width: 12.2 mm
- In inches: 0.48 in
- Oval
- Length x width: 15.1 x 10.4 mm
- In inches: 0.59 x 0.41 in
- Cushion
- Length x width: 10.6 x 10.6 mm
- In inches: 0.42 x 0.42 in
- Princess
- Length x width: 10.4 x 10.4 mm
- In inches: 0.41 x 0.41 in
- Emerald cut
- Length x width: 13.2 x 9.4 mm
- In inches: 0.52 x 0.37 in
- Asscher
- Length x width: 10.4 x 10.4 mm
- In inches: 0.41 x 0.41 in
- Radiant
- Length x width: 12.3 x 9.4 mm
- In inches: 0.48 x 0.37 in
- Pear
- Length x width: 16.0 x 10.4 mm
- In inches: 0.63 x 0.41 in
- Marquise
- Length x width: 19.6 x 9.8 mm
- In inches: 0.77 x 0.39 in
- Heart
- Length x width: 12.3 x 12.3 mm
- In inches: 0.48 x 0.48 in
- Trillion
- Length x width: 13.2 x 13.2 mm
- In inches: 0.52 x 0.52 in
- Baguette
- Length x width: 15.1 x 7.5 mm
- In inches: 0.59 x 0.30 in
4 carat opal against other gems
- Diamond
- Round, 4 carat: 10.2 mm
- Moissanite
- Round, 4 carat: 10.5 mm
- Sapphire
- Round, 4 carat: 9.8 mm
- Ruby
- Round, 4 carat: 9.8 mm
- Emerald
- Round, 4 carat: 11.2 mm
- Aquamarine
- Round, 4 carat: 11.2 mm
- Morganite
- Round, 4 carat: 11.1 mm
- Tanzanite
- Round, 4 carat: 10.4 mm
- Opal (this page)
- Round, 4 carat: 12.2 mm
4 carat opal on a finger
- 4
- Finger width: 14.9 mm
- Round covers: 82%
- Oval covers: 70%
- 5
- Finger width: 15.7 mm
- Round covers: 77%
- Oval covers: 66%
- 6
- Finger width: 16.5 mm
- Round covers: 74%
- Oval covers: 63%
- 7
- Finger width: 17.3 mm
- Round covers: 70%
- Oval covers: 60%
- 8
- Finger width: 18.1 mm
- Round covers: 67%
- Oval covers: 57%
- 9
- Finger width: 18.9 mm
- Round covers: 64%
- Oval covers: 55%
Opal at nearby weights
- 3 carat opal
- Round diameter: 11.1 mm
- 4 ct (this page)
- Round diameter: 12.2 mm
- 5 carat opal
- Round diameter: 13.1 mm
Questions
A round 4 carat opal is about 12.2 mm across. Other shapes are longer than they are wide: an oval is 15.1 x 10.4 mm.
Yes. A round 4 carat opal is 19% wider than a 4 carat diamond (10.2 mm).
0.80 grams. A carat is 200 milligrams for every gem.
A round 4 carat opal covers 74% of the width of a size 6 finger. Compare it with a ring you have tried on in the finger chart above.