Diamond Carat Size Chart: 0.5 to 5 Carats in Millimeters, on the Hand and in Lab-Grown Prices

By Cameron Malakan, owner of Clairamor and third-generation jeweler · Updated September 25, 2026

A carat is a weight, 0.2 grams, not a size, but for a well-cut round diamond the two track closely: a half carat is about 5.2 mm across, 1 carat 6.4 to 6.5 mm, 1.5 carats 7.3 to 7.4 mm, 2 carats 8.1 to 8.2 mm, 3 carats 9.3 mm, 4 carats 10.2 mm and 5 carats 11 mm. On a size 6 finger those cover 31%, 39%, 45%, 49%, 56%, 62% and 67% of the finger's width. In our picker on September 25, 2026, lab-grown rounds of D to G color and IF to VS2 clarity started at $360 for a half carat, $640 for 1 carat, $923 for 1.5, $1,178 for 2, $1,698 for 3, $2,195 for 4 and $2,711 for 5. This chart gives every size in millimeters for each shape we set, shows what each weight looks like on different hands, puts a lab-grown price on every step, and explains the two things carat numbers hide: spread, and total carat weight.

Round lab-grown diamond solitaire engagement ring in 14k white gold, angled view — Our round solitaire. The same setting takes anything from a half carat to five, and the head is built to the stone you choose.

Diamond carat size at a glance

Carats	Round, across	Face-up area vs 1 ct	Share of a size 6 finger	Lab-grown, our picker	With our 14k solitaire ($950)
0.5	5.1 to 5.2 mm	0.65x	31%	$360	$1,310
0.75	5.8 to 5.9 mm	0.8x	35%	$504	$1,454
1	6.4 to 6.5 mm	1x	39%	$640	$1,590
1.5	7.3 to 7.4 mm	1.3x	45%	$923	$1,873
2	8.1 to 8.2 mm	1.6x	49%	$1,178	$2,128
3	9.3 mm	2.1x	56%	$1,698	$2,648
4	10.2 mm	2.5x	62%	$2,195	$3,145
5	11 mm	3x	67%	$2,711	$3,661

Prices are the least expensive round of that weight in our picker on September 25, 2026, D to G color, IF to VS2 clarity, Very Good cut or better; the half carat is a 0.57 ct and the three quarter a 0.71 ct. Finger share is the diamond's diameter against the 16.5 mm width of a size 6 finger.

What a carat is, and what it is not

A carat is a fifth of a gram, 200 milligrams, and it is divided into 100 points, so a 0.50 carat diamond is a "fifty pointer" and the "1/10 carat" on a pendant tag is a 10-point stone about 3 mm across. The word comes from the carob seed, which traders once used as a counterweight, and it has been a fixed metric unit since 1907. Two things follow from carat being a weight. The first is that size depends on how the weight is cut: a deep stone hides weight below the girdle where you cannot see it, so a 1.20 carat can face up the same size as a well-cut 1 carat, and a round, an oval and an emerald cut of exactly 1 carat are three different sizes. The second is that carat weight is the one grade you cannot argue with. A laboratory report states it to a hundredth, the stone is weighed on a scale, and our picker lists the weight and the millimeter measurements side by side, which is the only way to compare stones properly. Our guide to the 4Cs covers how carat sits alongside cut, color and clarity.

Diamond carat size chart: rounds in millimeters

A round brilliant cut to good proportions is the one shape with a reliable carat-to-millimeter conversion, because its geometry is fixed. The chart gives the typical diameter at each weight, and the measurements of a real stone of about that weight in our picker on September 25, 2026, so you can see how close the two run; the picker's stones are lab-grown, cut Very Good or better, and every one lists its own measurements.

Carats	Typical diameter	A real stone in our picker	Its price
0.25	4.0 to 4.1 mm	0.34 ct, 4.5 mm	$228
0.4	4.7 to 4.8 mm	0.42 ct, 4.9 mm	$276
0.5	5.1 to 5.2 mm	0.57 ct, 5.4 mm	$360
0.75	5.8 to 5.9 mm	0.71 ct, 5.7 mm	$504
0.9	6.2 to 6.3 mm	0.91 ct, 6.3 mm	$510
1	6.4 to 6.5 mm	1.00 ct, 6.4 mm	$640
1.25	6.9 to 7.0 mm	1.22 ct, 6.9 mm	$761
1.5	7.3 to 7.4 mm	1.50 ct, 7.3 mm	$923
1.75	7.7 to 7.8 mm	1.71 ct, 7.7 mm	$1,064
2	8.1 to 8.2 mm	2.02 ct, 8.1 mm	$1,178
2.5	8.7 to 8.8 mm	2.50 ct, 8.7 mm	$1,422
3	9.3 to 9.4 mm	3.15 ct, 9.3 mm	$1,698
4	10.2 to 10.4 mm	4.02 ct, 10.2 mm	$2,195
5	11.0 to 11.2 mm	5.01 ct, 11.0 mm	$2,711
6	11.6 to 11.8 mm	6.00 ct, 11.6 mm	$3,162
7	12.3 to 12.5 mm	7.02 ct, 12.4 mm	$3,917
10	13.9 to 14.2 mm	10.01 ct, 13.9 mm	$6,649

0.5 ct
5.2 mm

1 ct
6.4 mm

1.5 ct
7.3 mm

2 ct
8.1 mm

3 ct
9.3 mm

4 ct
10.2 mm

5 ct
11.0 mm

Size 6 finger
16.5 mm across

Round diamonds from a half carat to five, drawn to one scale, beside the width of a size 6 finger. Screens differ, so treat it as a comparison rather than a ruler: doubling the carats adds about a quarter to the width.

Carat size by shape: 1, 1.5, 2 and 3 carats in millimeters

Fancy shapes spread their weight differently, so the same carat weight is a different size in each, and even within one shape the length varies with the proportions the cutter chose. Rather than a theoretical chart, this table gives the measurements of the least expensive stone of each weight and shape in our picker on September 25, 2026, length by width, so you are looking at real diamonds; expect other stones of the same weight to vary by half a millimeter or so.

Shape	1 carat	1.5 carats	2 carats	3 carats
Round	6.4 mm	7.3 mm	8.1 mm	9.3 mm
Oval	8.3 x 5.6 mm	9.0 x 6.6 mm	10.1 x 7.1 mm	11.9 x 8.0 mm
Emerald	6.8 x 4.6 mm	7.8 x 5.3 mm	8.6 x 6.0 mm	10.5 x 6.6 mm
Cushion	7.1 x 5.3 mm	7.1 x 6.2 mm	8.5 x 6.6 mm	10.3 x 7.6 mm
Radiant	7.5 x 5.0 mm	8.2 x 5.9 mm	8.9 x 6.4 mm	10.7 x 7.1 mm
Pear	8.9 x 5.7 mm	10.2 x 6.5 mm	11.4 x 7.0 mm	12.1 x 7.8 mm
Marquise	10.2 x 5.3 mm	11.4 x 6.0 mm	13.0 x 6.6 mm	15.6 x 7.5 mm
Moval	7.6 x 5.3 mm	10.4 x 6.2 mm	10.7 x 6.3 mm	14.3 x 7.2 mm

Two patterns are worth knowing before you choose a shape by size. Long shapes look biggest for the weight: a 1 carat marquise is 10 mm long and a 1 carat pear 9 mm, against 6.4 mm for a round, and because the length runs up the finger the eye reads them as larger than their face-up area justifies; the Dutch marquise, the straight-sided marquise, is covered in its own guide. Deep shapes look smallest: an emerald cut or a square cushion carries much of its weight in the pavilion, so a 2 carat emerald at 8.6 by 6 mm covers less of the finger than a 2 carat oval at 10.1 by 7.1; our cushion cut guide measures square and elongated cushions against the round at every weight. Our guide to which diamond shape looks the biggest ranks all of them, and the size comparison simulator draws any shape at any weight on a hand.

What each carat weight looks like on the hand

The finger sets the scale. The inside diameter of a ring is a fair measure of the finger's width at the base: a US size 4 is 14.9 mm across, a size 5 15.7 mm, a size 6 16.5 mm, a size 7 17.3 mm, a size 8 18.1 mm and a size 9 19 mm, so the same stone covers a third more of a size 4 finger than of a size 9. The table gives the share of the finger's width a round diamond covers at each size; for an elongated shape, use the width for how much of the finger it covers and the length for how far it runs up the finger.

Round diamond	Size 4 (14.9 mm)	Size 6 (16.5 mm)	Size 8 (18.1 mm)	How it reads
0.5 ct, 5.2 mm	35%	31%	29%	Delicate; a real diamond that does not announce itself
0.75 ct, 5.9 mm	40%	35%	33%	The classic "nice ring" size of a generation ago
1 ct, 6.4 mm	43%	39%	35%	Clearly a diamond from across a table; the size most people picture
1.5 ct, 7.3 mm	49%	44%	40%	Noticeably more than a carat; the lab-grown sweet spot for many hands
2 ct, 8.1 mm	54%	49%	45%	Half the finger; a big diamond on any hand
3 ct, 9.3 mm	62%	56%	51%	Unmistakably large; a statement on a slim hand
4 ct, 10.2 mm	68%	62%	56%	Very large; suits a broader hand or a size 7 and up
5 ct, 11 mm	74%	67%	61%	Two thirds of the finger; a ring you dress around

Height matters as much as width once you pass 2 carats. A 1 carat round is about 4 mm deep from girdle to point, a 2 carat 5 mm, a 3 carat 5.7 mm and a 4 carat 6.3 mm, so each step stands taller in the same setting; a bezel or low-profile setting takes some of that back, and a hidden halo turns the height into a feature. Band width changes the impression too: a 1.8 mm band makes any stone look bigger, and a 2.5 to 3 mm band makes a 2 carat and up look balanced. Our guide to how big an engagement ring should be takes hand size, lifestyle and proportion together.

1 carat vs 1.5 vs 2 carats: how much bigger is bigger?

Carats mislead here, because weight grows faster than width. Going from 1 carat to 1.5 adds 50% to the weight but only 14% to the diameter, 6.4 mm to 7.3 mm, which is about 30% more face-up area; going from 1.5 to 2 adds another 11% in width and 23% in area; and 1 carat to 2 carats, a doubling of weight, is 27% wider and 60% more face. Each step is visible, none is dramatic, and the first step is the one you notice most: the difference between a 1 carat and a 1.5 carat on the same hand is plain, while 1.5 to 2 is a matter of degree. In lab-grown the price steps are gentle too, $640 to $923 to $1,178 in our picker for rounds, so the honest advice is to compare the millimeters, not the carats, and to look at both sizes on your own finger in the simulator. For the step from 2 carats to 3, and the question of going further, our guide to how big a 3 carat diamond is has the numbers.

Lab-grown diamond prices by carat

Lab-grown pricing has one feature mined pricing lacks: it climbs gently. A mined diamond's price per carat jumps at the "magic sizes", a half carat, three quarters, 1 carat, 1.5, 2 and 3, because the rough for a bigger stone is exponentially rarer; a lab-grown diamond costs what it costs to grow and cut, which rises roughly with size. The table shows the least expensive stone at each weight in our picker on September 25, 2026, D to G color, IF to VS2 clarity, round and oval, and what each makes with our 14k solitaire.

Carats	Round, from	Oval, from	Round solitaire, 14k, complete	Price per carat, round
0.5	$360	–	$1,310	$630
1	$640	$719	$1,590	$640
1.5	$923	$900	$1,873	$615
2	$1,178	$1,193	$2,128	$583
2.5	$1,422	$1,494	$2,372	$569
3	$1,698	$1,724	$2,648	$539
4	$2,195	$2,334	$3,145	$546
5	$2,711	$2,673	$3,661	$541

Read the last column and you will see the odd truth of lab-grown pricing: the price per carat falls as the stone gets bigger, from about $640 at 1 carat to about $540 at 3 carats and beyond, the opposite of mined diamonds, where a 3 carat costs several times more per carat than a 1 carat. The one small jump is at the 1 carat line itself, where a 0.91 carat was $510 and a 1.00 carat $640, so a "just under" stone still saves a little. For context, Brilliant Earth's carat guide, as of September 2026, lists a lab-grown 1 carat at $3,500, a 2 carat at $7,500 and a 3 carat at $13,000; the same weights in our picker are $640, $1,178 and $1,698, because we sell the stone at the picker price and the setting at its own. The lab-grown diamond pricing guide explains how color and clarity move these numbers, and the price calculator estimates any combination. To answer two questions people ask a search engine: at our prices, $5,000 buys a 5 carat round solitaire with $1,300 to spare, and $2,000 buys a 1.5 carat.

The 4 carat and 5 carat question

Because the price curve is flat, more people than ever search for 4 and 5 carat lab-grown diamonds, and the answer is about the hand rather than the wallet. A 4 carat round is 10.2 mm across and 6.3 mm deep; it covers 62% of a size 6 finger and 56% of a size 8, and stands 2.3 mm taller than a 1 carat. A 5 carat is 11 mm and 6.7 mm deep, two thirds of an average finger. Both are beautiful on a broad hand, a size 7 and up, with a band of 2.5 mm or more and a setting built to the stone, and both are a lot of diamond on a slim size 4 or 5, where a 3 carat already reads as very large. Elongated shapes make the choice easier: a 4 carat oval (about 12.9 by 8.9 mm in our picker) or pear reads as enormous lengthwise while covering only about half the finger's width. Our 4 carat lab-grown rounds started at $2,195 on September 25, 2026, and 5 carats at $2,711, so the question to bring to a consultation is not whether you can, but whether you want a ring that wears like a ring or one that wears like an event.

Where the money goes: carat against the other Cs

With a mined diamond, the classic advice is to give up color and clarity to afford carats. With lab-grown the trade flips, because color and clarity are cheap: we stock D to G and IF to VS2 only, and at these prices there is no reason to go lower, so the grades that show, color in a big stone and clarity in a step cut, cost little to get right. Our VS1 vs VS2 guide prices every clarity grade at 1, 2 and 3 carats. That leaves two things worth paying attention to. Cut, because a poorly cut stone hides weight you paid for below the girdle; our picker opens on Very Good cut and better, and the measurements tell you the rest. And spread, which is the millimeters you get for the carats: two 1 carat rounds can measure 6.2 mm and 6.6 mm, and the second one looks like a 1.15 carat for the same money. Compare stones by millimeters and depth, not by carat weight alone; a round with a depth of 59 to 63% and a table of 54 to 60% is spending its weight where you can see it. Our guides to VVS1 clarity and SI clarity explain where the clarity lines are.

Total carat weight is not the center stone

A ring described as "2 carats total weight", or 2 ctw, may have a 1 carat center with a carat of small diamonds around it, or a three quarter carat center in a heavy halo. Total carat weight is a legitimate figure, but it is not the size of the diamond on top, and it is the number most likely to mislead. Ask for the center stone's weight and measurements, and its own report. Our settings are priced without the center stone, so the price you see on a hidden halo or a three stone setting covers the setting and its small diamonds, and the center is the stone you choose from the picker, with its own report and its own weight.

How to make a diamond look bigger

If the budget sets the carats, the setting sets the impression. An elongated shape, oval, pear, marquise, elongated radiant or emerald cut, gives the most length per carat. A thinner band, 1.8 to 2 mm, makes the stone look larger by contrast, and a hidden halo adds sparkle and apparent width under the stone without a visible frame; a full bezel does the opposite and makes a diamond look slightly smaller, which is its one cost. Prongs matter: four slim prongs show more stone than six heavy ones. A white metal under a white stone lets the edge disappear into the setting. And a clean diamond looks a size bigger than a dirty one, which is the cheapest upgrade there is. Our guide to choosing a diamond shape covers the trade-offs shape by shape.

Where Clairamor fits

Every ring we make starts with a stone you choose from our picker, where each diamond is listed with its weight, its measurements and its IGI or GIA report, so you can compare a 1.5 carat against a 2 carat by the millimeters that matter. We stock D to G color and IF to VS2 clarity only, and the setting price is the setting without the center stone, so a 14k solitaire at $950 with a 1.5 carat round at $923 is a $1,873 ring. Every ring carries a lifetime warranty against manufacturing defects, comes with an appraisal for insurance, and includes one complimentary resize within 100 days for clients in the USA. If you are between two sizes, book a consultation.

Choose a lab-grown diamond by carat Engagement ring settings See any size on a hand

Not sure which carat weight is right? Book a design consultation.

Frequently asked questions

How big is a 1 carat diamond?

A well-cut 1 carat round is 6.4 to 6.5 mm across and about 4 mm deep, and covers 39% of a size 6 finger. A 1 carat oval is about 8 by 5.5 mm, an emerald 6.8 by 4.6, a pear 9 by 5.7 and a marquise 10 by 5.3. In Clairamor's picker a 1 carat round of D to G color and IF to VS2 clarity started at $640 on September 25, 2026.

How big is a 2 carat diamond?

A 2 carat round is 8.1 to 8.2 mm across, 27% wider than a 1 carat and about 60% more face-up area, and it covers about half of a size 6 finger. A 2 carat oval is about 10 by 7 mm, a pear 11.4 by 7, a marquise 13 by 6.6 and an emerald 8.6 by 6. In lab-grown a 2 carat round started at $1,178 in Clairamor's picker on September 25, 2026.

Is a 2 carat diamond big?

Yes. A 2 carat round spans half the width of an average finger and is noticed across a room; on a size 4 or 5 hand it is a statement, on a size 8 a comfortable large stone. It is also the size at which height starts to matter, at about 5 mm deep, so band width and setting choice do more work than at 1 carat.

What is the perfect diamond carat size?

There is no perfect size, only a proportion. On most hands 1 to 1.5 carats reads as a clear, classic diamond, 2 carats as big and 3 as very big. The right answer depends on finger size, how the hand is used and what the setting adds; a 1.5 carat on a size 5 finger looks like a 2 carat on a size 8. In lab-grown the price difference between the sizes is small enough that most people choose by look, not budget.

How many carats is a $5,000 diamond?

In a mined diamond of good quality, about 1 carat. In a lab-grown diamond from Clairamor's picker on September 25, 2026, $5,000 bought a 7 carat round loose, and a 5 carat round solitaire in 14k gold, stone and setting together, came to $3,661. A more useful question is what $2,000 to $3,000 buys as a finished ring: a 1.5 carat round solitaire was $1,873 and a 3 carat $2,648.

What does 1/10 carat mean?

A tenth of a carat, 10 points, a diamond about 3 mm across and 0.02 grams in weight, the size used for accent stones and small pendants. Carats are divided into 100 points, so a half carat is 50 points and a 1/4 carat is 25 points, about 4 mm across.

Is carat a size or a weight?

A weight: one carat is 0.2 grams. Size follows from weight and shape, so a 1 carat round is 6.4 mm across while a 1 carat marquise is 10 mm long, and a deeply cut stone of any shape looks smaller than a well-cut one of the same weight. That is why a diamond's measurements matter as much as its carats.

Does a 1.5 carat look much bigger than a 1 carat?

Noticeably, yes. The diameter goes from 6.4 mm to 7.3 mm, about 14% wider and 30% more face-up area, and on the same hand the difference is plain. It is the most visible single step in the carat range; the step from 1.5 to 2 carats is a matter of degree by comparison.

How much is a 1 carat lab-grown diamond?

In Clairamor's picker on September 25, 2026, the least expensive 1 carat round of D to G color and IF to VS2 clarity was $640, and the least expensive 1 carat oval $719; with the 14k solitaire at $950 that is a finished ring from $1,590. Higher color and clarity add a hundred or two.

What is total carat weight?

The combined weight of every diamond on the ring, the center stone and all the accents. A "2 ctw" ring can have a 1 carat center, or a smaller one in a heavier halo. Always ask for the center stone's own weight and measurements; at Clairamor the center stone is chosen separately, with its own report, and the setting price covers the setting and its accent diamonds.

Which carat size is most popular for an engagement ring?

Across the US, 1 to 1.5 carats has long been the most common center stone. In lab-grown rings the center of gravity has moved up, because a 2 carat costs less than a 1 carat mined stone once did, so 1.5 to 2 carats is now a common choice and 3 carats is no longer unusual.