Princess vs Radiant diamond size

By HeyGema™ · Updated November 5, 2026

In short

A 1 carat princess measures 5.5 x 5.5 mm and a 1 carat radiant 6.5 x 5.0 mm. At the same weight a radiant faces up about 6% larger than a princess. In face-up terms, 1 carat of princess looks like a 0.88 carat round and 1 carat of radiant like a 0.96 carat round.

5.5 x 5.5 mm1 ct princess
6.5 x 5.0 mm1 ct radiant
+6%radiant face-up vs princess

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 princess

5.5 x 5.5 mm

1 ct radiant

6.5 x 5.0 mm

Side by side

1 ct princess inside 1 ct radiant

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

Princess vs Radiant diamond size at the same weight

At the same weight a radiant faces up about 6% larger than a princess. A 1 carat princess measures 5.5 x 5.5 mm and a 1 carat radiant 6.5 x 5.0 mm. A 1 carat princess faces up like a 0.88 carat round, and a 1 carat radiant like a 0.96 carat round.

0.5 carat: Princess length x width: 4.4 x 4.4 mm; Radiant length x width: 5.2 x 4.0 mm; Radiant face-up vs princess: +6%

0.75 carat: Princess length x width: 5.0 x 5.0 mm; Radiant length x width: 5.9 x 4.5 mm; Radiant face-up vs princess: +6%

1 carat: Princess length x width: 5.5 x 5.5 mm; Radiant length x width: 6.5 x 5.0 mm; Radiant face-up vs princess: +6%

1.5 carat: Princess length x width: 6.3 x 6.3 mm; Radiant length x width: 7.4 x 5.7 mm; Radiant face-up vs princess: +6%

2 carat: Princess length x width: 6.9 x 6.9 mm; Radiant length x width: 8.2 x 6.3 mm; Radiant face-up vs princess: +6%

3 carat: Princess length x width: 7.9 x 7.9 mm; Radiant length x width: 9.4 x 7.2 mm; Radiant face-up vs princess: +6%

Carat	Princess length x width	Radiant length x width	Radiant face-up vs princess
0.5 carat	4.4 x 4.4 mm	5.2 x 4.0 mm	+6%
0.75 carat	5.0 x 5.0 mm	5.9 x 4.5 mm	+6%
1 carat	5.5 x 5.5 mm	6.5 x 5.0 mm	+6%
1.5 carat	6.3 x 6.3 mm	7.4 x 5.7 mm	+6%
2 carat	6.9 x 6.9 mm	8.2 x 6.3 mm	+6%
3 carat	7.9 x 7.9 mm	9.4 x 7.2 mm	+6%

Princess vs Radiant on a finger

A 1 carat princess covers 33% 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 princess covers: 42%; 1.5 ct radiant covers: 38%

5: Finger width: 15.7 mm; 1.5 ct princess covers: 40%; 1.5 ct radiant covers: 36%

6: Finger width: 16.5 mm; 1.5 ct princess covers: 38%; 1.5 ct radiant covers: 35%

7: Finger width: 17.3 mm; 1.5 ct princess covers: 36%; 1.5 ct radiant covers: 33%

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

US ring size	Finger width	1.5 ct princess covers	1.5 ct radiant covers
4	14.9 mm	42%	38%
5	15.7 mm	40%	36%
6	16.5 mm	38%	35%
7	17.3 mm	36%	33%
8	18.1 mm	35%	32%

Match the look, not only the carat

Because a radiant of about 0.91 carat faces up like 1 carat of princess, comparing by weight alone hides the difference. Compare millimeters, or put both stones side by side in the size comparison tool.

Princess and Radiant size charts

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

Questions

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

A 1 carat princess is about 5.5 x 5.5 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 princess is 6.9 x 6.9 mm and a 2 carat radiant is 8.2 x 6.3 mm. Face-up, the radiant is +6% against the princess.

A 1 carat princess covers 33% 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.