How big is a 1 carat round diamond?
By HeyGema™ · Updated
In short
A 1 carat round diamond measures about 6.5 mm. On a size 6 finger it covers 39% of the width. For the same weight, a round diamond is 6.5 mm.
- 6.5 mm1 carat round
- 0.25 inthe same in inches
- referenceface-up size vs a round
- 39%of a size 6 finger's width
Carat to mm calculator
About 6.5 x 6.5 mm
An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.
1 ct round
6.5 mm
1 ct round
6.5 mm
Side by side
1 ct round inside 1 ct round
1 carat round diamond size
A well-cut 1 carat round diamond measures about 6.5 mm (0.25 inches) at a length-to-width ratio of 1.00:1. It weighs 0.20 grams.
1 carat round on a finger
- 4
- Finger width: 14.9 mm
- Round covers: 43%
- 5
- Finger width: 15.7 mm
- Round covers: 41%
- 6
- Finger width: 16.5 mm
- Round covers: 39%
- 7
- Finger width: 17.3 mm
- Round covers: 37%
- 8
- Finger width: 18.1 mm
- Round covers: 36%
- 9
- Finger width: 18.9 mm
- Round covers: 34%
Round sizes near 1 carat
- 0.5 carat
- Length x width: 5.1 mm
- Round of the same weight: 5.1 mm
- 0.75 carat
- Length x width: 5.9 mm
- Round of the same weight: 5.9 mm
- 1 (this page)
- Length x width: 6.5 mm
- Round of the same weight: 6.5 mm
- 1.25 carat
- Length x width: 6.9 mm
- Round of the same weight: 6.9 mm
- 1.5 carat
- Length x width: 7.4 mm
- Round of the same weight: 7.4 mm
1 carat in other shapes
Every row is a well-cut diamond of 1 carat. The last column is the face-up size against the round.
- Oval
- Length x width: 8.0 x 5.5 mm
- Against round: +6%
- Cushion
- Length x width: 5.6 x 5.6 mm
- Against round: -14%
- Princess
- Length x width: 5.5 x 5.5 mm
- Against round: -8%
- Emerald cut
- Length x width: 7.0 x 5.0 mm
- Against round: +4%
- Asscher
- Length x width: 5.5 x 5.5 mm
- Against round: -16%
- Radiant
- Length x width: 6.5 x 5.0 mm
- Against round: -2%
- Pear
- Length x width: 8.5 x 5.5 mm
- Against round: -3%
- Marquise
- Length x width: 10.4 x 5.2 mm
- Against round: +16%
- Heart
- Length x width: 6.5 x 6.5 mm
- Against round: -17%
- Trillion
- Length x width: 7.0 x 7.0 mm
- Against round: -14%
- Baguette
- Length x width: 8.0 x 4.0 mm
- Against round: -2%
Questions
A 1 carat round diamond is about 6.5 mm at the usual 1.00:1 ratio.
A 1 carat round diamond is about 0.25 inches across.
There is no rule. The stone is 43% of the width of a size 4 finger and 36% 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.