1 carat vs 3 carat diamond size
By HeyGema™ · Updated
In short
A round 3 carat diamond measures 9.3 mm and a round 1 carat 6.5 mm. The 3 carat is three times the weight but only 44% wider (2.9 mm), with 108% more face-up area.
- 6.5 vs 9.3 mmround diameter
- 44%wider at 3 ct
- 108%more face-up area
Carat to mm calculator
About 9.3 x 9.3 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
1 carat vs 3 carat: how much bigger is it?
A 3 carat diamond weighs three times the weight of a 1 carat, but it is only 44% wider. A round 1 carat measures 6.5 mm and a round 3 carat 9.3 mm, a difference of 2.9 mm. Seen from above, the 3 carat covers 108% 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.
1 carat and 3 carat in every shape
- Round
- 1 carat: 6.5 mm
- 3 carat: 9.3 mm
- Longer by: 2.9 mm
- Oval
- 1 carat: 8.0 x 5.5 mm
- 3 carat: 11.5 x 7.9 mm
- Longer by: 3.5 mm
- Cushion
- 1 carat: 5.6 x 5.6 mm
- 3 carat: 8.1 x 8.1 mm
- Longer by: 2.5 mm
- Princess
- 1 carat: 5.5 x 5.5 mm
- 3 carat: 7.9 x 7.9 mm
- Longer by: 2.4 mm
- Emerald cut
- 1 carat: 7.0 x 5.0 mm
- 3 carat: 10.1 x 7.2 mm
- Longer by: 3.1 mm
- Pear
- 1 carat: 8.5 x 5.5 mm
- 3 carat: 12.3 x 7.9 mm
- Longer by: 3.8 mm
- Marquise
- 1 carat: 10.4 x 5.2 mm
- 3 carat: 15.0 x 7.5 mm
- Longer by: 4.6 mm
- Radiant
- 1 carat: 6.5 x 5.0 mm
- 3 carat: 9.4 x 7.2 mm
- Longer by: 2.9 mm
- Asscher
- 1 carat: 5.5 x 5.5 mm
- 3 carat: 7.9 x 7.9 mm
- Longer by: 2.4 mm
- Heart
- 1 carat: 6.5 x 6.5 mm
- 3 carat: 9.4 x 9.4 mm
- Longer by: 2.9 mm
1 carat vs 3 carat on a finger
- 4
- Finger width: 14.9 mm
- Round 1 ct covers: 43%
- Round 3 ct covers: 63%
- 5
- Finger width: 15.7 mm
- Round 1 ct covers: 41%
- Round 3 ct covers: 59%
- 6
- Finger width: 16.5 mm
- Round 1 ct covers: 39%
- Round 3 ct covers: 56%
- 7
- Finger width: 17.3 mm
- Round 1 ct covers: 37%
- Round 3 ct covers: 54%
- 8
- Finger width: 18.1 mm
- Round 1 ct covers: 36%
- Round 3 ct covers: 51%
On a size 6 finger the 1 carat reads as classic (39% of the width) and the 3 carat as bold (56%). 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 1 and 3 carat
Shape changes the picture. An oval or a pear of 1 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.