3 carat vs 4 carat diamond size
By HeyGema™ · Updated
In short
A round 4 carat diamond measures 10.2 mm and a round 3 carat 9.3 mm. The 4 carat is 1.33 times the weight but only 10% wider (0.9 mm), with 21% more face-up area.
- 9.3 vs 10.2 mmround diameter
- 10%wider at 4 ct
- 21%more face-up area
Carat to mm calculator
About 10.2 x 10.2 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
3 carat vs 4 carat: how much bigger is it?
A 4 carat diamond weighs 1.33 times the weight of a 3 carat, but it is only 10% wider. A round 3 carat measures 9.3 mm and a round 4 carat 10.2 mm, a difference of 0.9 mm. Seen from above, the 4 carat covers 21% more area.
The gap is smaller than the weights suggest because carats measure weight, which grows with volume. A stone that is twice as heavy is the cube root of two (1.26 times) as wide, not twice as wide.
3 carat and 4 carat in every shape
- Round
- 3 carat: 9.3 mm
- 4 carat: 10.2 mm
- Longer by: 0.9 mm
- Oval
- 3 carat: 11.5 x 7.9 mm
- 4 carat: 12.7 x 8.7 mm
- Longer by: 1.2 mm
- Cushion
- 3 carat: 8.1 x 8.1 mm
- 4 carat: 8.9 x 8.9 mm
- Longer by: 0.8 mm
- Princess
- 3 carat: 7.9 x 7.9 mm
- 4 carat: 8.7 x 8.7 mm
- Longer by: 0.8 mm
- Emerald cut
- 3 carat: 10.1 x 7.2 mm
- 4 carat: 11.1 x 7.9 mm
- Longer by: 1.0 mm
- Pear
- 3 carat: 12.3 x 7.9 mm
- 4 carat: 13.5 x 8.7 mm
- Longer by: 1.2 mm
- Marquise
- 3 carat: 15.0 x 7.5 mm
- 4 carat: 16.5 x 8.3 mm
- Longer by: 1.5 mm
- Radiant
- 3 carat: 9.4 x 7.2 mm
- 4 carat: 10.3 x 7.9 mm
- Longer by: 0.9 mm
- Asscher
- 3 carat: 7.9 x 7.9 mm
- 4 carat: 8.7 x 8.7 mm
- Longer by: 0.8 mm
- Heart
- 3 carat: 9.4 x 9.4 mm
- 4 carat: 10.3 x 10.3 mm
- Longer by: 0.9 mm
3 carat vs 4 carat on a finger
- 4
- Finger width: 14.9 mm
- Round 3 ct covers: 63%
- Round 4 ct covers: 69%
- 5
- Finger width: 15.7 mm
- Round 3 ct covers: 59%
- Round 4 ct covers: 65%
- 6
- Finger width: 16.5 mm
- Round 3 ct covers: 56%
- Round 4 ct covers: 62%
- 7
- Finger width: 17.3 mm
- Round 3 ct covers: 54%
- Round 4 ct covers: 59%
- 8
- Finger width: 18.1 mm
- Round 3 ct covers: 51%
- Round 4 ct covers: 56%
On a size 6 finger the 3 carat reads as bold (56% of the width) and the 4 carat as statement (62%). The bands are our own: delicate is under 30% of the finger's width, classic is 30% to 44%, bold is 45% to 59%, statement is 60% and more.
Other cuts at 3 and 4 carat
Shape changes the picture. An oval or a pear of 3 carat can face up as large as a round of a higher weight. See the shapes that look biggest, or compare any two stones with the size comparison tool.