1 carat vs 1.25 carat diamond size
By HeyGema™ · Updated
In short
A round 1.25 carat diamond measures 6.9 mm and a round 1 carat 6.5 mm. The 1.25 carat is 1.25 times the weight but only 8% wider (0.5 mm), with 16% more face-up area.
- 6.5 vs 6.9 mmround diameter
- 8%wider at 1.25 ct
- 16%more face-up area
Carat to mm calculator
About 6.9 x 6.9 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
1 carat vs 1.25 carat: how much bigger is it?
A 1.25 carat diamond weighs 1.25 times the weight of a 1 carat, but it is only 8% wider. A round 1 carat measures 6.5 mm and a round 1.25 carat 6.9 mm, a difference of 0.5 mm. Seen from above, the 1.25 carat covers 16% 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 1.25 carat in every shape
- Round
- 1 carat: 6.5 mm
- 1.25 carat: 6.9 mm
- Longer by: 0.5 mm
- Oval
- 1 carat: 8.0 x 5.5 mm
- 1.25 carat: 8.6 x 5.9 mm
- Longer by: 0.6 mm
- Cushion
- 1 carat: 5.6 x 5.6 mm
- 1.25 carat: 6.0 x 6.0 mm
- Longer by: 0.4 mm
- Princess
- 1 carat: 5.5 x 5.5 mm
- 1.25 carat: 5.9 x 5.9 mm
- Longer by: 0.4 mm
- Emerald cut
- 1 carat: 7.0 x 5.0 mm
- 1.25 carat: 7.5 x 5.4 mm
- Longer by: 0.5 mm
- Pear
- 1 carat: 8.5 x 5.5 mm
- 1.25 carat: 9.2 x 5.9 mm
- Longer by: 0.7 mm
- Marquise
- 1 carat: 10.4 x 5.2 mm
- 1.25 carat: 11.2 x 5.6 mm
- Longer by: 0.8 mm
- Radiant
- 1 carat: 6.5 x 5.0 mm
- 1.25 carat: 7.0 x 5.4 mm
- Longer by: 0.5 mm
- Asscher
- 1 carat: 5.5 x 5.5 mm
- 1.25 carat: 5.9 x 5.9 mm
- Longer by: 0.4 mm
- Heart
- 1 carat: 6.5 x 6.5 mm
- 1.25 carat: 7.0 x 7.0 mm
- Longer by: 0.5 mm
1 carat vs 1.25 carat on a finger
- 4
- Finger width: 14.9 mm
- Round 1 ct covers: 43%
- Round 1.25 ct covers: 47%
- 5
- Finger width: 15.7 mm
- Round 1 ct covers: 41%
- Round 1.25 ct covers: 44%
- 6
- Finger width: 16.5 mm
- Round 1 ct covers: 39%
- Round 1.25 ct covers: 42%
- 7
- Finger width: 17.3 mm
- Round 1 ct covers: 37%
- Round 1.25 ct covers: 40%
- 8
- Finger width: 18.1 mm
- Round 1 ct covers: 36%
- Round 1.25 ct covers: 38%
On a size 6 finger the 1 carat reads as classic (39% of the width) and the 1.25 carat as classic (42%). 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 1.25 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.