How many carats is a 2.5 mm diamond?

By HeyGema™ · Updated November 5, 2026

In short

A 2.5 mm round diamond weighs about 0.058 carat (0.012 grams). A 2.5 mm princess cut weighs about 0.090 carat, and an oval that is 2.5 mm long about 0.030 carat.

0.058 ctround diamond, 2.5 mm
0.012 gweight
0.10 in2.5 mm in inches

Carat to mm calculator

ShapeGemLength (mm)

About 0.06 carat

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

2.5 mm diamond weight by shape

The weight of a well-cut diamond measuring 2.5 mm. For round and square shapes the number is the diameter or the side. For longer shapes it is the long side, with the width following the usual ratio.

Round: Size: 2.5 mm; Weight: 0.058 ct

Oval: Size: 2.5 mm x 1.72 mm; Weight: 0.031 ct

Cushion: Size: 2.5 mm x 2.50 mm; Weight: 0.089 ct

Princess: Size: 2.5 mm x 2.50 mm; Weight: 0.094 ct

Emerald cut: Size: 2.5 mm x 1.79 mm; Weight: 0.046 ct

Asscher: Size: 2.5 mm x 2.50 mm; Weight: 0.094 ct

Radiant: Size: 2.5 mm x 1.92 mm; Weight: 0.057 ct

Pear: Size: 2.5 mm x 1.61 mm; Weight: 0.025 ct

Marquise: Size: 2.5 mm x 1.25 mm; Weight: 0.014 ct

Heart: Size: 2.5 mm x 2.50 mm; Weight: 0.057 ct

Trillion: Size: 2.5 mm x 2.50 mm; Weight: 0.046 ct

Baguette: Size: 2.5 mm x 1.25 mm; Weight: 0.031 ct

Shape	Size	Weight
Round	2.5 mm	0.058 ct
Oval	2.5 mm x 1.72 mm	0.031 ct
Cushion	2.5 mm x 2.50 mm	0.089 ct
Princess	2.5 mm x 2.50 mm	0.094 ct
Emerald cut	2.5 mm x 1.79 mm	0.046 ct
Asscher	2.5 mm x 2.50 mm	0.094 ct
Radiant	2.5 mm x 1.92 mm	0.057 ct
Pear	2.5 mm x 1.61 mm	0.025 ct
Marquise	2.5 mm x 1.25 mm	0.014 ct
Heart	2.5 mm x 2.50 mm	0.057 ct
Trillion	2.5 mm x 2.50 mm	0.046 ct
Baguette	2.5 mm x 1.25 mm	0.031 ct

2.5 mm stones in other gems

A round stone of the same size weighs differently in each gem, because gems differ in density.

Diamond: Weight of a round stone: 0.058 ct

Moissanite: Weight of a round stone: 0.053 ct

Sapphire: Weight of a round stone: 0.066 ct

Ruby: Weight of a round stone: 0.066 ct

Emerald: Weight of a round stone: 0.045 ct

Aquamarine: Weight of a round stone: 0.045 ct

Topaz: Weight of a round stone: 0.058 ct

Amethyst: Weight of a round stone: 0.044 ct

Spinel: Weight of a round stone: 0.060 ct

Tanzanite: Weight of a round stone: 0.055 ct

Morganite: Weight of a round stone: 0.046 ct

Gem	Weight of a round stone
Diamond	0.058 ct
Moissanite	0.053 ct
Sapphire	0.066 ct
Ruby	0.066 ct
Emerald	0.045 ct
Aquamarine	0.045 ct
Topaz	0.058 ct
Amethyst	0.044 ct
Spinel	0.060 ct
Tanzanite	0.055 ct
Morganite	0.046 ct

2.5 mm diamond studs

A pair of 2.5 mm round diamond studs has a total carat weight of about 0.12 carat, 0.058 carat for each stone. See the diamond stud earring size chart.

Nearby sizes

1.5 mm: Weight: 0.013 ct; Inches: 0.06 in

2 mm: Weight: 0.030 ct; Inches: 0.08 in

2.5 mm (this page): Weight: 0.058 ct; Inches: 0.10 in

3 mm: Weight: 0.1 ct; Inches: 0.12 in

3.5 mm: Weight: 0.16 ct; Inches: 0.14 in

Diameter	Weight	Inches
1.5 mm	0.013 ct	0.06 in
2 mm	0.030 ct	0.08 in
2.5 mm (this page)	0.058 ct	0.10 in
3 mm	0.1 ct	0.12 in
3.5 mm	0.16 ct	0.14 in

Questions

About 0.058 carat for a well-cut round diamond.

A 2.5 mm princess cut, measured along one side, weighs about 0.090 carat.

A 2.5 mm round moissanite is labeled 0.058 carat (diamond equivalent weight) and weighs about 0.050 carat. See the moissanite size chart.

2.5 mm is 0.10 inches.