Cushion vs Princess diamond size

By HeyGema™ · Updated November 5, 2026

In short

A 1 carat cushion measures 5.6 x 5.6 mm and a 1 carat princess 5.5 x 5.5 mm. At the same weight a princess faces up about 7% larger than a cushion. In face-up terms, 1 carat of cushion looks like a 0.80 carat round and 1 carat of princess like a 0.88 carat round.

5.6 x 5.6 mm1 ct cushion
5.5 x 5.5 mm1 ct princess
+7%princess face-up vs cushion

Carat to mm calculator

ShapeGemCarat

About 5.5 x 5.5 mm

An estimate for a well-cut stone. A deep or shallow cut faces up smaller or bigger.

1 ct cushion

5.6 x 5.6 mm

1 ct princess

5.5 x 5.5 mm

Side by side

1 ct princess inside 1 ct cushion

A 1 carat cushion and a 1 carat princess diamond, to the same scale.

Cushion vs Princess diamond size at the same weight

At the same weight a princess faces up about 7% larger than a cushion. A 1 carat cushion measures 5.6 x 5.6 mm and a 1 carat princess 5.5 x 5.5 mm. A 1 carat cushion faces up like a 0.80 carat round, and a 1 carat princess like a 0.88 carat round.

0.5 carat: Cushion length x width: 4.4 x 4.4 mm; Princess length x width: 4.4 x 4.4 mm; Princess face-up vs cushion: +7%

0.75 carat: Cushion length x width: 5.1 x 5.1 mm; Princess length x width: 5.0 x 5.0 mm; Princess face-up vs cushion: +7%

1 carat: Cushion length x width: 5.6 x 5.6 mm; Princess length x width: 5.5 x 5.5 mm; Princess face-up vs cushion: +7%

1.5 carat: Cushion length x width: 6.4 x 6.4 mm; Princess length x width: 6.3 x 6.3 mm; Princess face-up vs cushion: +7%

2 carat: Cushion length x width: 7.1 x 7.1 mm; Princess length x width: 6.9 x 6.9 mm; Princess face-up vs cushion: +7%

3 carat: Cushion length x width: 8.1 x 8.1 mm; Princess length x width: 7.9 x 7.9 mm; Princess face-up vs cushion: +7%

Carat	Cushion length x width	Princess length x width	Princess face-up vs cushion
0.5 carat	4.4 x 4.4 mm	4.4 x 4.4 mm	+7%
0.75 carat	5.1 x 5.1 mm	5.0 x 5.0 mm	+7%
1 carat	5.6 x 5.6 mm	5.5 x 5.5 mm	+7%
1.5 carat	6.4 x 6.4 mm	6.3 x 6.3 mm	+7%
2 carat	7.1 x 7.1 mm	6.9 x 6.9 mm	+7%
3 carat	8.1 x 8.1 mm	7.9 x 7.9 mm	+7%

Cushion vs Princess on a finger

A 1 carat cushion covers 34% of the width of a size 6 finger and a 1 carat princess 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 princess on a size 6 finger.

4: Finger width: 14.9 mm; 1.5 ct cushion covers: 43%; 1.5 ct princess covers: 42%

5: Finger width: 15.7 mm; 1.5 ct cushion covers: 41%; 1.5 ct princess covers: 40%

6: Finger width: 16.5 mm; 1.5 ct cushion covers: 39%; 1.5 ct princess covers: 38%

7: Finger width: 17.3 mm; 1.5 ct cushion covers: 37%; 1.5 ct princess covers: 36%

8: Finger width: 18.1 mm; 1.5 ct cushion covers: 35%; 1.5 ct princess covers: 35%

US ring size	Finger width	1.5 ct cushion covers	1.5 ct princess covers
4	14.9 mm	43%	42%
5	15.7 mm	41%	40%
6	16.5 mm	39%	38%
7	17.3 mm	37%	36%
8	18.1 mm	35%	35%

Match the look, not only the carat

Because a princess of about 0.90 carat faces up like 1 carat of cushion, comparing by weight alone hides the difference. Compare millimeters, or put both stones side by side in the size comparison tool.

Cushion and Princess size charts

Full charts from 0.25 to 5 carat: Cushion diamond size chart and Princess diamond size chart.

Questions

At the same weight a princess faces up about 7% larger than a cushion. Face-up area is what you see from above; the princess has more of it at equal weight.

A 1 carat cushion is about 5.6 x 5.6 mm and a 1 carat princess about 5.5 x 5.5 mm, for a well-cut stone at the usual ratio.

A 2 carat cushion is 7.1 x 7.1 mm and a 2 carat princess is 6.9 x 6.9 mm. Face-up, the princess is +7% against the cushion.

A 1 carat cushion covers 34% of the width of a size 6 finger and a 1 carat princess 33%. The numbers change with ring size and with the stone's length-to-width ratio.