Size guide · mm to carat

Diamond Size Chart: mm to Carat for Every Shape

How big is a 1, 2 or 3 carat diamond, and how many carats is a 3mm or 8mm diamond? These sizes come from the diamonds in our own inventory, measured shape by shape.

Based on Guru Diam inventory · 5,000+ certified diamonds measured · October 12, 2026

12Shapes

0.5–5+ ctCertified sizes

1–6 mmSmall rounds (approx.)

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Converter

Carat to mm, shape by shape

Shape Carat

Typical face-up size—

Outline drawn at about true size on a standard screen (screens vary). The dashed circle is a 1 carat round for comparison.

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See the size · real diamonds from our inventory

See Every Diamond Shape at 1, 2 and 3 Carats

Typical face-up size of our certified lab-grown diamonds, measured shape by shape. Hover a diamond to turn it in 360°, tap through to shop that shape.

↻ 360°

Round lab-grown diamond, IGI certified, face-up

Round1,000+

1 ct	6.4 × 6.5 mm
2 ct	8.1 × 8.1 mm
3 ct	9.3 × 9.3 mm

Shop Round

↻ 360°

Oval lab-grown diamond, IGI certified, face-up

Oval100+

1 ct	8.3 × 5.6 mm
2 ct	10.3 × 7.1 mm
3 ct	11.7 × 8.2 mm

Shop Oval

↻ 360°

Emerald Cut lab-grown diamond, IGI certified, face-up

Emerald Cut500+

1 ct	7.0 × 4.7 mm
2 ct	8.7 × 5.9 mm
3 ct	9.9 × 6.8 mm

Shop Emerald Cut

↻ 360°

Radiant Cut lab-grown diamond, IGI certified, face-up

Radiant Cut500+

1 ct	7.2 × 5.0 mm
2 ct	8.9 × 6.3 mm
3 ct	9.9 × 7.2 mm

Shop Radiant Cut

↻ 360°

Cushion lab-grown diamond, IGI certified, face-up

Cushion100+

1 ct	6.0 × 5.9 mm
2 ct	8.6 × 6.8 mm
3 ct	9.9 × 7.6 mm

Shop Cushion

↻ 360°

Pear lab-grown diamond, IGI certified, face-up

Pear100+

1 ct	9.1 × 5.7 mm
2 ct	11.2 × 7.0 mm
3 ct	12.8 × 8.0 mm

Shop Pear

↻ 360°

Princess lab-grown diamond, IGI certified, face-up

Princess100+

1 ct	5.6 × 5.6 mm
2 ct	6.9 × 6.8 mm
3 ct	7.9 × 7.8 mm

Shop Princess

↻ 360°

Marquise lab-grown diamond, IGI certified, face-up

Marquise100+

1 ct	10.3 × 5.2 mm
2 ct	12.9 × 6.5 mm
3 ct	14.9 × 7.5 mm

Shop Marquise

↻ 360°

Heart lab-grown diamond, IGI certified, face-up

Heart100+

1 ct	6.2 × 7.0 mm
2 ct	7.7 × 8.8 mm
3 ct	9.0 × 10.1 mm

Shop Heart

↻ 360°

Asscher lab-grown diamond, IGI certified, face-up

Asscher100+

1 ct	5.6 × 5.6 mm
2 ct	7.0 × 7.0 mm
3 ct	8.0 × 8.0 mm

Shop Asscher

↻ 360°

Old Miner lab-grown diamond, IGI certified, face-up

Old Miner500+

1 ct	7.6 × 5.1 mm
2 ct	9.5 × 6.5 mm
3 ct	10.8 × 7.5 mm

Shop Old Miner

↻ 360°

Hexagon lab-grown diamond, IGI certified, face-up

Hexagon500+

1 ct	9.1 × 4.5 mm
2 ct	11.2 × 6.3 mm
3 ct	12.8 × 7.2 mm

Shop Hexagon

Median sizes from our certified lab-grown diamonds

Diamond Size Chart by Shape and Carat

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	7.03 × 7.08 mm	1.35 ct	500+	1.00–1.49 ct RoundShop →
1.50–1.99 ct	7.91 × 7.96 mm	1.87 ct	500+	1.50–1.99 ct RoundShop →
2.00–2.49 ct	8.16 × 8.20 mm	2.07 ct	100+	2.00–2.49 ct RoundShop →
2.50–2.99 ct	9.13 × 9.17 mm	2.85 ct	100+	2.50–2.99 ct RoundShop →
3.00–3.99 ct	9.34 × 9.38 mm	3.10 ct	100+	3.00–3.99 ct RoundShop →
4.00–4.99 ct	10.25 × 10.30 mm	4.09 ct	50+	4.00–4.99 ct RoundShop →
5.00+ ct	11.55 × 11.62 mm	6.01 ct	10+	5.00+ ct RoundShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	8.46 × 5.87 mm	1.11 ct	100+	1.00–1.49 ct OvalShop →
1.50–1.99 ct	9.52 × 6.59 mm	1.59 ct	50+	1.50–1.99 ct OvalShop →
2.00–2.49 ct	10.43 × 7.17 mm	2.08 ct	10+	2.00–2.49 ct OvalShop →
2.50–2.99 ct	11.14 × 7.65 mm	2.57 ct	10+	2.50–2.99 ct OvalShop →
3.00–3.99 ct	12.06 × 8.29 mm	3.13 ct	10+	3.00–3.99 ct OvalShop →
4.00–4.99 ct	13.00 × 8.96 mm	4.08 ct	10+	4.00–4.99 ct OvalShop →
5.00+ ct	15.47 × 10.65 mm	7.00 ct	10+	5.00+ ct OvalShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
0.50–0.69 ct	6.01 × 4.04 mm	0.67 ct	In stock	0.50–0.69 ct Emerald CutShop →
1.00–1.49 ct	7.16 × 4.87 mm	1.11 ct	100+	1.00–1.49 ct Emerald CutShop →
1.50–1.99 ct	8.05 × 5.44 mm	1.58 ct	100+	1.50–1.99 ct Emerald CutShop →
2.00–2.49 ct	8.81 × 5.99 mm	2.10 ct	50+	2.00–2.49 ct Emerald CutShop →
2.50–2.99 ct	9.49 × 6.38 mm	2.57 ct	50+	2.50–2.99 ct Emerald CutShop →
3.00–3.99 ct	10.24 × 7.06 mm	3.52 ct	10+	3.00–3.99 ct Emerald CutShop →
4.00–4.99 ct	11.02 × 7.58 mm	4.14 ct	10+	4.00–4.99 ct Emerald CutShop →
5.00+ ct	12.90 × 8.94 mm	7.08 ct	50+	5.00+ ct Emerald CutShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	7.33 × 5.18 mm	1.11 ct	100+	1.00–1.49 ct Radiant CutShop →
1.50–1.99 ct	8.31 × 5.74 mm	1.58 ct	100+	1.50–1.99 ct Radiant CutShop →
2.00–2.49 ct	8.92 × 6.38 mm	2.08 ct	50+	2.00–2.49 ct Radiant CutShop →
2.50–2.99 ct	8.14 × 7.59 mm	2.58 ct	50+	2.50–2.99 ct Radiant CutShop →
3.00–3.99 ct	10.04 × 7.56 mm	3.14 ct	50+	3.00–3.99 ct Radiant CutShop →
4.00–4.99 ct	11.24 × 8.11 mm	4.07 ct	10+	4.00–4.99 ct Radiant CutShop →
5.00+ ct	12.75 × 9.01 mm	5.81 ct	10+	5.00+ ct Radiant CutShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	6.47 × 5.95 mm	1.13 ct	50+	1.00–1.49 ct CushionShop →
1.50–1.99 ct	7.19 × 6.69 mm	1.58 ct	100+	1.50–1.99 ct CushionShop →
2.00–2.49 ct	8.66 × 6.84 mm	2.11 ct	50+	2.00–2.49 ct CushionShop →
2.50–2.99 ct	9.27 × 7.26 mm	2.60 ct	50+	2.50–2.99 ct CushionShop →
3.00–3.99 ct	9.83 × 8.15 mm	3.28 ct	50+	3.00–3.99 ct CushionShop →
4.00–4.99 ct	11.21 × 8.39 mm	4.05 ct	10+	4.00–4.99 ct CushionShop →
5.00+ ct	12.86 × 10.66 mm	8.03 ct	10+	5.00+ ct CushionShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
0.90–0.99 ct	8.79 × 5.32 mm	0.92 ct	In stock	0.90–0.99 ct PearShop →
1.00–1.49 ct	9.59 × 5.97 mm	1.21 ct	100+	1.00–1.49 ct PearShop →
1.50–1.99 ct	10.40 × 6.60 mm	1.64 ct	100+	1.50–1.99 ct PearShop →
2.00–2.49 ct	11.43 × 7.18 mm	2.09 ct	10+	2.00–2.49 ct PearShop →
2.50–2.99 ct	12.43 × 7.73 mm	2.60 ct	10+	2.50–2.99 ct PearShop →
3.00–3.99 ct	13.03 × 8.11 mm	3.08 ct	10+	3.00–3.99 ct PearShop →
4.00–4.99 ct	14.49 × 9.20 mm	4.55 ct	10+	4.00–4.99 ct PearShop →
5.00+ ct	16.70 × 10.30 mm	6.53 ct	50+	5.00+ ct PearShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	6.10 × 6.05 mm	1.39 ct	10+	1.00–1.49 ct PrincessShop →
1.50–1.99 ct	6.59 × 6.55 mm	1.78 ct	100+	1.50–1.99 ct PrincessShop →
2.00–2.49 ct	7.13 × 7.08 mm	2.21 ct	10+	2.00–2.49 ct PrincessShop →
2.50–2.99 ct	7.56 × 7.49 mm	2.59 ct	10+	2.50–2.99 ct PrincessShop →
3.00–3.99 ct	8.16 × 8.05 mm	3.26 ct	10+	3.00–3.99 ct PrincessShop →
4.00–4.99 ct	8.90 × 8.71 mm	4.12 ct	10+	4.00–4.99 ct PrincessShop →
5.00+ ct	9.79 × 9.76 mm	5.81 ct	10+	5.00+ ct PrincessShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	11.19 × 5.62 mm	1.25 ct	50+	1.00–1.49 ct MarquiseShop →
1.50–1.99 ct	12.37 × 6.19 mm	1.71 ct	50+	1.50–1.99 ct MarquiseShop →
2.00–2.49 ct	13.11 × 6.65 mm	2.08 ct	10+	2.00–2.49 ct MarquiseShop →
2.50–2.99 ct	14.32 × 7.24 mm	2.65 ct	10+	2.50–2.99 ct MarquiseShop →
3.00–3.99 ct	15.27 × 7.85 mm	3.40 ct	10+	3.00–3.99 ct MarquiseShop →
4.00–4.99 ct	16.59 × 8.38 mm	4.07 ct	10+	4.00–4.99 ct MarquiseShop →
5.00+ ct	18.69 × 9.35 mm	6.02 ct	50+	5.00+ ct MarquiseShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	6.33 × 7.12 mm	1.09 ct	50+	1.00–1.49 ct HeartShop →
1.50–1.99 ct	7.23 × 8.11 mm	1.61 ct	50+	1.50–1.99 ct HeartShop →
2.00–2.49 ct	7.77 × 8.95 mm	2.10 ct	10+	2.00–2.49 ct HeartShop →
2.50–2.99 ct	8.49 × 9.59 mm	2.60 ct	10+	2.50–2.99 ct HeartShop →
3.00–3.99 ct	9.00 × 10.20 mm	3.09 ct	10+	3.00–3.99 ct HeartShop →
4.00–4.99 ct	9.71 × 11.19 mm	4.10 ct	In stock	4.00–4.99 ct HeartShop →
5.00+ ct	11.33 × 13.01 mm	7.01 ct	In stock	5.00+ ct HeartShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	5.76 × 5.72 mm	1.18 ct	10+	1.00–1.49 ct AsscherShop →
1.50–1.99 ct	6.54 × 6.49 mm	1.70 ct	10+	1.50–1.99 ct AsscherShop →
2.00–2.49 ct	7.09 × 7.05 mm	2.10 ct	10+	2.00–2.49 ct AsscherShop →
2.50–2.99 ct	7.57 × 7.55 mm	2.57 ct	10+	2.50–2.99 ct AsscherShop →
3.00–3.99 ct	8.35 × 8.27 mm	3.45 ct	10+	3.00–3.99 ct AsscherShop →
4.00–4.99 ct	8.93 × 8.92 mm	4.12 ct	10+	4.00–4.99 ct AsscherShop →
5.00+ ct	10.48 × 10.43 mm	7.05 ct	10+	5.00+ ct AsscherShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	7.94 × 5.48 mm	1.26 ct	100+	1.00–1.49 ct Old MinerShop →
1.50–1.99 ct	8.71 × 5.97 mm	1.60 ct	100+	1.50–1.99 ct Old MinerShop →
2.00–2.49 ct	9.53 × 6.57 mm	2.10 ct	100+	2.00–2.49 ct Old MinerShop →
2.50–2.99 ct	10.32 × 7.08 mm	2.59 ct	10+	2.50–2.99 ct Old MinerShop →
3.00–3.99 ct	10.90 × 7.52 mm	3.14 ct	100+	3.00–3.99 ct Old MinerShop →
4.00–4.99 ct	12.08 × 8.30 mm	4.23 ct	10+	4.00–4.99 ct Old MinerShop →
5.00+ ct	13.78 × 9.51 mm	6.56 ct	100+	5.00+ ct Old MinerShop →

Carat range	Median face-up (L × W)	Median carat	Diamonds measured	Shop this size
1.00–1.49 ct	9.33 × 4.66 mm	1.13 ct	50+	1.00–1.49 ct HexagonShop →
1.50–1.99 ct	10.53 × 5.28 mm	1.61 ct	50+	1.50–1.99 ct HexagonShop →
2.00–2.49 ct	11.35 × 6.05 mm	2.10 ct	100+	2.00–2.49 ct HexagonShop →
2.50–2.99 ct	12.45 × 6.27 mm	2.62 ct	10+	2.50–2.99 ct HexagonShop →
3.00–3.99 ct	13.12 × 7.23 mm	3.13 ct	50+	3.00–3.99 ct HexagonShop →
4.00–4.99 ct	14.50 × 7.29 mm	4.24 ct	10+	4.00–4.99 ct HexagonShop →
5.00+ ct	16.81 × 8.22 mm	6.45 ct	100+	5.00+ ct HexagonShop →

On the hand

How Big Does a 1, 2, 3 or 5 Carat Diamond Look?

The sizes under each ring are the median face-up measurements of that shape and carat in our inventory. The hand photos are illustrations to show scale; the films are our own pieces from inventory.

a 1 carat round diamond solitaire on a hand, illustrative — **1 ct round**Typical face-up 6.4 × 6.5 mm

a 2 carat oval diamond solitaire on a hand, illustrative — **2 ct oval**Typical face-up 10.3 × 7.1 mm

a 3 carat emerald-cut diamond solitaire on a hand, illustrative — **3 ct emerald cut**Typical face-up 9.9 × 6.8 mm

a 5 carat cushion-cut diamond solitaire on a hand, illustrative — **5 ct cushion**

SolitaireOur inventory

Three-stoneOur inventory

Eternity bandOur inventory

StudsOur inventory

Antique & colorOur inventory

Hand photos: illustrative (AI-generated for this page). Films: Guru Diam pieces from our inventory (Right Click videos).

Calibrated round melee diamonds from 1 to 3 mm in rows on indigo, with tweezers, illustrative

Melee & pointers

Small Round Diamonds, Sold by the Millimetre

For pavé, halos and side work, buy by diameter. Every parcel is calibrated so the diamonds match across a setting.

1.0 mm≈ 0.004 ct each (approx.)
2.0 mm≈ 0.03 ct each (approx.)
3.0 mm≈ 0.10 ct each (approx.)
±0.05–0.10 mmMatched melee tolerance

Shop round melee & pointers →See the 1–6 mm table

Small rounds · approx.

Round Diamond mm to Carat (1–6 mm)

Melee and pointers are sold by the mm. Weights below are estimates for a well-proportioned round brilliant.

Diameter	Approx. carat each	Our melee
1.0 mm	≈ 0.004 ct	In stock
1.3 mm	≈ 0.008 ct	In stock
1.5 mm	≈ 0.013 ct	In stock
1.8 mm	≈ 0.022 ct	In stock
2.0 mm	≈ 0.030 ct	In stock
2.2 mm	≈ 0.040 ct	In stock
2.5 mm	≈ 0.058 ct	In stock
2.7 mm	≈ 0.073 ct	In stock
3.0 mm	≈ 0.100 ct	In stock
3.3 mm	≈ 0.134 ct	In stock
3.5 mm	≈ 0.160 ct	In stock
3.8 mm	≈ 0.204 ct	In stock
4.0 mm	≈ 0.238 ct	In stock
4.5 mm	≈ 0.339 ct	In stock
5.0 mm	≈ 0.465 ct	In stock
5.5 mm	≈ 0.619 ct	In stock
6.0 mm	≈ 0.804 ct	In stock

Round melee & pointers →

For writers, schools and jewelers

Cite This Chart

Free to reference. Please link to this page so readers get the updated sizes.

Suggested credit: “Diamond size chart by Guru Diam, based on measured inventory.”

Need a size you don't see?

We can source or cut diamonds to your specification.

Trade accounts approved the same business day if submitted before 4 PM ET.

Common questions

Diamond mm to Carat: Questions Jewelers Ask

How many carats is a 2mm diamond?

A 2mm round diamond weighs about 0.03 carat (approx., standard round brilliant proportions). Melee this size is sold by the mm, often in parcels.

How many carats is a 3mm diamond?

A 3mm round diamond is about 0.10 carat (approx.). A 3.5mm round is about 0.16 carat.

How many carats is a 4mm round diamond?

A 4mm round diamond weighs about 0.24 carat (approx.), and a 4.5mm round is about 0.34 carat.

How many carats is a 5mm, 6mm or 7mm round diamond?

Approximately 0.47 ct at 5mm, 0.80 ct at 6mm and 1.28 ct at 7mm. In our inventory, 1.00–1.49 carat rounds measure a median 7.03 mm across.

How many carats is an 8mm diamond?

An 8mm round is close to 2 carats. Our 2.00–2.49 carat rounds measure a median 8.16 mm across (100+ diamonds in stock). Other shapes differ: see the tables above.

How much bigger is a 2 carat diamond than a 1 carat?

In our round inventory, the 1.00–1.49 carat range measures a median 7.03 mm and the 2.00–2.49 range 8.16 mm, so doubling the weight adds roughly a quarter to the diameter, not double.

About this chart

How Big Is a 1, 2 or 3 Carat Diamond?

Carat is weight, not size, so two diamonds of the same carat can face up differently by shape and cut. This diamond size chart uses the median length and width of the certified lab-grown diamonds in our New York and Los Angeles inventory, so it reflects real, well-cut diamonds rather than a textbook ideal.

Use it to plan a setting, quote a client or match a center to side diamonds. Browse certified lab-grown diamonds by shape, or see all wholesale lab grown diamonds.