How big is a 0.25 carat heart shaped diamond?

By HeyGema™ · Updated November 5, 2026

In short

A 0.25 carat heart shaped diamond measures about 4.1 x 4.1 mm. It faces up 17% smaller than a round diamond of the same weight. On a size 6 finger it covers 25% of the width. For the same weight, a round diamond is 4.1 mm.

4.1 x 4.1 mm0.25 carat heart
0.16 x 0.16 inthe same in inches
-17%face-up size vs a round
25%of a size 6 finger's width

Carat to mm calculator

ShapeGemCarat

About 4.1 x 4.1 mm

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

0.25 ct heart

4.1 x 4.1 mm

0.25 ct round

4.1 mm

Side by side

0.25 ct round inside 0.25 ct heart

A 0.25 carat heart diamond beside a 0.25 carat round, to the same scale.

0.25 carat heart diamond size

A well-cut 0.25 carat heart shaped diamond measures about 4.1 x 4.1 mm (0.16 x 0.16 inches) at a length-to-width ratio of 1.00:1. It faces up 17% smaller than a round diamond of the same weight. It weighs 0.050 grams.

0.25 carat heart on a finger

4.1 mm stone on a 16.5 mm finger: it covers 25% of the widthA 0.25 carat heart diamond on a size 6 finger.

4: Finger width: 14.9 mm; Heart covers: 28%

5: Finger width: 15.7 mm; Heart covers: 26%

6: Finger width: 16.5 mm; Heart covers: 25%

7: Finger width: 17.3 mm; Heart covers: 24%

8: Finger width: 18.1 mm; Heart covers: 23%

9: Finger width: 18.9 mm; Heart covers: 22%

US ring size	Finger width	Heart covers
4	14.9 mm	28%
5	15.7 mm	26%
6	16.5 mm	25%
7	17.3 mm	24%
8	18.1 mm	23%
9	18.9 mm	22%

Heart sizes near 0.25 carat

0.25 (this page): Length x width: 4.1 x 4.1 mm; Round of the same weight: 4.1 mm

0.33 carat: Length x width: 4.5 x 4.5 mm; Round of the same weight: 4.5 mm

0.5 carat: Length x width: 5.2 x 5.2 mm; Round of the same weight: 5.1 mm

Carat	Length x width	Round of the same weight
0.25 (this page)	4.1 x 4.1 mm	4.1 mm
0.33 carat	4.5 x 4.5 mm	4.5 mm
0.5 carat	5.2 x 5.2 mm	5.1 mm

0.25 carat in other shapes

Every row is a well-cut diamond of 0.25 carat. The last column is the face-up size against the heart.

Round: Length x width: 4.1 mm; Against heart: +21%

Oval: Length x width: 5.0 x 3.5 mm; Against heart: +28%

Cushion: Length x width: 3.5 x 3.5 mm; Against heart: +4%

Princess: Length x width: 3.5 x 3.5 mm; Against heart: +11%

Emerald cut: Length x width: 4.4 x 3.1 mm; Against heart: +25%

Asscher: Length x width: 3.5 x 3.5 mm; Against heart: +2%

Radiant: Length x width: 4.1 x 3.1 mm; Against heart: +18%

Pear: Length x width: 5.4 x 3.5 mm; Against heart: +17%

Marquise: Length x width: 6.6 x 3.3 mm; Against heart: +40%

Trillion: Length x width: 4.4 x 4.4 mm; Against heart: +4%

Baguette: Length x width: 5.0 x 2.52 mm; Against heart: +18%

Shape	Length x width	Against heart
Round	4.1 mm	+21%
Oval	5.0 x 3.5 mm	+28%
Cushion	3.5 x 3.5 mm	+4%
Princess	3.5 x 3.5 mm	+11%
Emerald cut	4.4 x 3.1 mm	+25%
Asscher	3.5 x 3.5 mm	+2%
Radiant	4.1 x 3.1 mm	+18%
Pear	5.4 x 3.5 mm	+17%
Marquise	6.6 x 3.3 mm	+40%
Trillion	4.4 x 4.4 mm	+4%
Baguette	5.0 x 2.52 mm	+18%

Questions

A 0.25 carat heart shaped diamond is about 4.1 x 4.1 mm at the usual 1.00:1 ratio.

No. Face-up, a 0.25 carat heart is 17% smaller than a 0.25 carat round (4.1 mm).

There is no rule. The stone is 28% of the width of a size 4 finger and 23% 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.