Cushion vs Radiant 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 radiant 6.5 x 5.0 mm. At the same weight a radiant faces up about 14% larger than a cushion. In face-up terms, 1 carat of cushion looks like a 0.80 carat round and 1 carat of radiant like a 0.96 carat round.

5.6 x 5.6 mm1 ct cushion
6.5 x 5.0 mm1 ct radiant
+14%radiant face-up vs cushion

Carat to mm calculator

ShapeGemCaratLength to width

About 6.5 x 5.0 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 radiant

6.5 x 5.0 mm

Side by side

1 ct cushion inside 1 ct radiant

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

Cushion vs Radiant diamond size at the same weight

At the same weight a radiant faces up about 14% larger than a cushion. A 1 carat cushion measures 5.6 x 5.6 mm and a 1 carat radiant 6.5 x 5.0 mm. A 1 carat cushion faces up like a 0.80 carat round, and a 1 carat radiant like a 0.96 carat round.

0.5 carat: Cushion length x width: 4.4 x 4.4 mm; Radiant length x width: 5.2 x 4.0 mm; Radiant face-up vs cushion: +14%

0.75 carat: Cushion length x width: 5.1 x 5.1 mm; Radiant length x width: 5.9 x 4.5 mm; Radiant face-up vs cushion: +14%

1 carat: Cushion length x width: 5.6 x 5.6 mm; Radiant length x width: 6.5 x 5.0 mm; Radiant face-up vs cushion: +14%

1.5 carat: Cushion length x width: 6.4 x 6.4 mm; Radiant length x width: 7.4 x 5.7 mm; Radiant face-up vs cushion: +14%

2 carat: Cushion length x width: 7.1 x 7.1 mm; Radiant length x width: 8.2 x 6.3 mm; Radiant face-up vs cushion: +14%

3 carat: Cushion length x width: 8.1 x 8.1 mm; Radiant length x width: 9.4 x 7.2 mm; Radiant face-up vs cushion: +14%

Carat	Cushion length x width	Radiant length x width	Radiant face-up vs cushion
0.5 carat	4.4 x 4.4 mm	5.2 x 4.0 mm	+14%
0.75 carat	5.1 x 5.1 mm	5.9 x 4.5 mm	+14%
1 carat	5.6 x 5.6 mm	6.5 x 5.0 mm	+14%
1.5 carat	6.4 x 6.4 mm	7.4 x 5.7 mm	+14%
2 carat	7.1 x 7.1 mm	8.2 x 6.3 mm	+14%
3 carat	8.1 x 8.1 mm	9.4 x 7.2 mm	+14%

Cushion vs Radiant on a finger

A 1 carat cushion covers 34% of the width of a size 6 finger and a 1 carat radiant covers 30%. Long cuts sit along the finger, so their width is what shows across it.

5.7 mm stone on a 16.5 mm finger: it covers 35% of the widthA 1.5 carat radiant on a size 6 finger.

4: Finger width: 14.9 mm; 1.5 ct cushion covers: 43%; 1.5 ct radiant covers: 38%

5: Finger width: 15.7 mm; 1.5 ct cushion covers: 41%; 1.5 ct radiant covers: 36%

6: Finger width: 16.5 mm; 1.5 ct cushion covers: 39%; 1.5 ct radiant covers: 35%

7: Finger width: 17.3 mm; 1.5 ct cushion covers: 37%; 1.5 ct radiant covers: 33%

8: Finger width: 18.1 mm; 1.5 ct cushion covers: 35%; 1.5 ct radiant covers: 32%

US ring size	Finger width	1.5 ct cushion covers	1.5 ct radiant covers
4	14.9 mm	43%	38%
5	15.7 mm	41%	36%
6	16.5 mm	39%	35%
7	17.3 mm	37%	33%
8	18.1 mm	35%	32%

Match the look, not only the carat

Because a radiant of about 0.83 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 Radiant size charts

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

Questions

At the same weight a radiant faces up about 14% larger than a cushion. Face-up area is what you see from above; the radiant has more of it at equal weight.

A 1 carat cushion is about 5.6 x 5.6 mm and a 1 carat radiant about 6.5 x 5.0 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 radiant is 8.2 x 6.3 mm. Face-up, the radiant is +14% against the cushion.

A 1 carat cushion covers 34% of the width of a size 6 finger and a 1 carat radiant 30%. The numbers change with ring size and with the stone's length-to-width ratio.