Round vs Oval diamond size

By HeyGema™ · Updated November 5, 2026

In short

A 1 carat round measures 6.5 mm and a 1 carat oval 8.0 x 5.5 mm. At the same weight an oval faces up about 6% larger than a round. In face-up terms, 1 carat of round looks like a 1.00 carat round and 1 carat of oval like a 1.09 carat round.

6.5 mm1 ct round
8.0 x 5.5 mm1 ct oval
+6%oval face-up vs round

Carat to mm calculator

ShapeGemCaratLength to width

About 8.0 x 5.5 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 oval

8.0 x 5.5 mm

Side by side

1 ct round inside 1 ct oval

A 1 carat round and a 1 carat oval diamond, to the same scale.

Round vs Oval diamond size at the same weight

At the same weight an oval faces up about 6% larger than a round. A 1 carat round measures 6.5 mm and a 1 carat oval 8.0 x 5.5 mm. A 1 carat round faces up like a 1.00 carat round, and a 1 carat oval like a 1.09 carat round.

0.5 carat: Round length x width: 5.1 mm; Oval length x width: 6.3 x 4.4 mm; Oval face-up vs round: +6%

0.75 carat: Round length x width: 5.9 mm; Oval length x width: 7.3 x 5.0 mm; Oval face-up vs round: +6%

1 carat: Round length x width: 6.5 mm; Oval length x width: 8.0 x 5.5 mm; Oval face-up vs round: +6%

1.5 carat: Round length x width: 7.4 mm; Oval length x width: 9.2 x 6.3 mm; Oval face-up vs round: +6%

2 carat: Round length x width: 8.1 mm; Oval length x width: 10.1 x 6.9 mm; Oval face-up vs round: +6%

3 carat: Round length x width: 9.3 mm; Oval length x width: 11.5 x 7.9 mm; Oval face-up vs round: +6%

Carat	Round length x width	Oval length x width	Oval face-up vs round
0.5 carat	5.1 mm	6.3 x 4.4 mm	+6%
0.75 carat	5.9 mm	7.3 x 5.0 mm	+6%
1 carat	6.5 mm	8.0 x 5.5 mm	+6%
1.5 carat	7.4 mm	9.2 x 6.3 mm	+6%
2 carat	8.1 mm	10.1 x 6.9 mm	+6%
3 carat	9.3 mm	11.5 x 7.9 mm	+6%

Round vs Oval on a finger

A 1 carat round covers 39% of the width of a size 6 finger and a 1 carat oval covers 33%. Long cuts sit along the finger, so their width is what shows across it.

6.3 mm stone on a 16.5 mm finger: it covers 38% of the widthA 1.5 carat oval on a size 6 finger.

4: Finger width: 14.9 mm; 1.5 ct round covers: 50%; 1.5 ct oval covers: 42%

5: Finger width: 15.7 mm; 1.5 ct round covers: 47%; 1.5 ct oval covers: 40%

6: Finger width: 16.5 mm; 1.5 ct round covers: 45%; 1.5 ct oval covers: 38%

7: Finger width: 17.3 mm; 1.5 ct round covers: 43%; 1.5 ct oval covers: 36%

8: Finger width: 18.1 mm; 1.5 ct round covers: 41%; 1.5 ct oval covers: 35%

US ring size	Finger width	1.5 ct round covers	1.5 ct oval covers
4	14.9 mm	50%	42%
5	15.7 mm	47%	40%
6	16.5 mm	45%	38%
7	17.3 mm	43%	36%
8	18.1 mm	41%	35%

Match the look, not only the carat

Because an oval of about 0.92 carat faces up like 1 carat of round, comparing by weight alone hides the difference. Compare millimeters, or put both stones side by side in the size comparison tool.

Round and Oval size charts

Full charts from 0.25 to 5 carat: Round diamond size chart and Oval diamond size chart.

Questions

At the same weight an oval faces up about 6% larger than a round. Face-up area is what you see from above; the oval has more of it at equal weight.

A 1 carat round is about 6.5 mm and a 1 carat oval about 8.0 x 5.5 mm, for a well-cut stone at the usual ratio.

A 2 carat round is 8.1 mm and a 2 carat oval is 10.1 x 6.9 mm. Face-up, the oval is +6% against the round.

A 1 carat round covers 39% of the width of a size 6 finger and a 1 carat oval 33%. The numbers change with ring size and with the stone's length-to-width ratio.