JewelLoop · Diamond mm to carat chart

https://jewelloop.net/tools/diamond-mm-to-carat/

Estimates for guidance; verify before production.

Diamond mm to carat chart

Published millimetre-to-carat figures for round brilliants from 0.80 mm melee upwards, and for princess, oval, cushion, emerald, Asscher, radiant, pear, marquise, heart and trillion shapes.

Round brilliant, 0.80 to 5.00 mm

Weight per stone from published trade charts. “Typical” is the middle of the published figures; the range shows how far the charts differ, because cutters' proportions differ.

Diameter	Typical (ct)	Published range (ct)	Sources
0.80 mm	0.0025	0.0024–0.0025	D M
0.90 mm	0.0032	0.003–0.0034	G M
1.00 mm	0.0048	0.004–0.005	D G M S
1.10 mm	0.006	0.005–0.0062	G K M
1.20 mm	0.0076	0.006–0.008	G K M S
1.30 mm	0.01	0.008–0.01	D G K M S
1.40 mm	0.012	0.01–0.012	G K M
1.50 mm	0.015	0.012–0.0154	D G K M S
1.60 mm	0.0179	0.015–0.018	G K M
1.70 mm	0.0204	0.018–0.021	G K M S
1.80 mm	0.025	0.02–0.025	D G K M S
1.90 mm	0.0286	0.025–0.029	G K M
2.00 mm	0.03	0.03–0.035	D G K M S
2.10 mm	0.037	0.035–0.04	G K M S
2.20 mm	0.042	0.04–0.0454	G K M S
2.30 mm	0.0531	0.052–0.0541	K M
2.40 mm	0.054	0.05–0.0589	G K M S
2.50 mm	0.06	0.06–0.069	D G K M S
2.60 mm	0.0715	0.069–0.074	K M
2.70 mm	0.072	0.07–0.078	G K M S
2.80 mm	0.0817	0.08–0.086	G K M S
2.90 mm	0.0925	0.09–0.0952	G K M S
3.00 mm	0.101	0.10–0.11	D G K M S
3.10 mm	0.112	0.11–0.116	G K M S
3.20 mm	0.125	0.12–0.13	G K M S
3.30 mm	0.14	0.14–0.145	G K M S
3.40 mm	0.15	0.149–0.155	G K M S
3.50 mm	0.161	0.16–0.17	D G K M S
3.60 mm	0.177	0.17–0.19	G K M S
3.70 mm	0.198	0.18–0.20	G K M S
3.80 mm	0.217	0.20–0.22	G M S
3.90 mm	0.225	0.22–0.23	G S
4.00 mm	0.25	0.23–0.25	B D G M
4.10 mm	0.25	0.25	G S
4.20 mm	0.285	0.27–0.30	G S
4.30 mm	≈ 0.303	0.27–0.33	between published sizes*
4.40 mm	0.32	0.31–0.33	G S
4.50 mm	0.36	0.36	D
4.60 mm	0.37	0.36–0.38	G S
4.70 mm	≈ 0.385	0.36–0.40	between published sizes*
4.80 mm	0.40	0.40	G S
4.90 mm	≈ 0.443	0.40–0.50	between published sizes*
5.00 mm	0.485	0.46–0.50	B D G S

* No published chart lists this size. Shown halfway between the sizes above and below it.

Round brilliant, over 5 mm

5.2 mm 0.50 ct S

5.4 mm 0.60 ct S

5.6 mm 0.65 ct S

5.7 mm 0.75 ct S

6.0 mm 0.80 ct S

6.3 mm 0.95 ct S

6.4 mm 1.00 ct S

6.6 mm 1.10 ct S

6.8 mm 1.17 ct S

7.0 mm 1.25 ct S

7.2 mm 1.33 ct S

7.3 mm 1.50 ct B

7.5 mm 1.60 ct S

7.8 mm 1.75 ct S

7.9 mm 1.90 ct S

8.0 mm 2.00 ct S

8.3 mm 2.15 ct S

8.4 mm 2.25 ct S

8.6 mm 2.50 ct S

9.3 mm 3.00 ct S

9.4 mm 3.15 ct S

9.6 mm 3.35 ct S

9.8 mm 3.50 ct S

10.0 mm 3.75 ct S

10.2 mm 4.00 ct S

10.3 mm 4.25 ct S

10.5 mm 4.50 ct S

10.7 mm 4.75 ct S

11.0 mm 5.00 ct S

Fancy shapes

Length × width in millimetres for common carat weights, as published by Stuller from the stones it stocks (source S). Proportions vary by cutter, so measure the stone you have.

Shape

Princess (square)

0.0075 ct 1×1 mm

0.015 ct 1.25×1.25 mm

0.025 ct 1.5×1.5 mm

0.035 ct 1.75×1.75 mm

0.05 ct 2×2 mm

0.07 ct 2.25×2.25 mm

0.09 ct 2.5×2.5 mm

0.11 ct 2.75×2.75 mm

0.16 ct 3×3 mm

0.20 ct 3.25×3.25 mm

0.25 ct 3.5×3.5 mm

0.33 ct 3.75×3.75 mm

0.40 ct 4×4 mm

0.47 ct 4.3×4.3 mm

0.50 ct 4.5×4.5 mm

0.60 ct 4.65×4.65 mm

0.75 ct 4.75×4.75 mm

0.80 ct 4.8×4.8 mm

0.95 ct 5×5 mm

1.00 ct 5.5×5.5 mm

1.25 ct 6×6 mm

1.50 ct 6.5×6.5 mm

2.00 ct 7×7 mm

2.25 ct 7.25×7.25 mm

2.50 ct 7.5×7.5 mm

3.00 ct 8×8 mm

4.00 ct 9×9 mm

5.00 ct 9.5×9.5 mm

Oval

0.05 ct 3×2.3 mm

0.10 ct 3.6×2.7 mm

0.16 ct 4×3 mm

0.22 ct 4.5×3.5 mm

0.25 ct 5×3.5 mm

0.33 ct 5×4 mm

0.38 ct 6×4 mm

0.50 ct 6.25×4.5 mm

0.75 ct 7×5 mm

1.00 ct 8×6 mm

1.50 ct 9×6.5 mm

2.00 ct 10×7 mm

3.00 ct 11.5×8 mm

3.50 ct 12×8.5 mm

4.00 ct 12.5×9 mm

5.00 ct 13.6×10 mm

Cushion

0.16 ct 3×3 mm

0.20 ct 3.3×3.3 mm

0.25 ct 3.6×3.6 mm

0.33 ct 3.8×3.8 mm

0.40 ct 4.25×4.25 mm

0.50 ct 4.5×4.5 mm

0.75 ct 5.25×5.25 mm

1.00 ct 5.6×5.6 mm

1.10 ct 6×6 mm

1.25 ct 6.25×6.25 mm

1.50 ct 6.5×6.5 mm

2.00 ct 7×7 mm

2.50 ct 7.25×7.25 mm

3.00 ct 8.2×8.2 mm

4.00 ct 8.7×8.7 mm

5.00 ct 9.7×9.7 mm

Emerald cut

0.10 ct 3×2.3 mm

0.16 ct 3.75×2.5 mm

0.20 ct 3.75×2.75 mm

0.25 ct 4×3 mm

0.30 ct 5×3 mm

0.33 ct 4.5×3 mm

0.40 ct 5×3.5 mm

0.50 ct 5.5×4 mm

0.75 ct 6×4.5 mm

1.00 ct 6.5×5 mm

1.50 ct 7.5×5.5 mm

2.00 ct 8.5×6 mm

3.00 ct 9.5×7 mm

4.00 ct 10.5×8 mm

5.00 ct 11.5×8.5 mm

Asscher

0.05 ct 2×2 mm

0.07 ct 2.3×2.3 mm

0.10 ct 2.6×2.6 mm

0.16 ct 3×3 mm

0.20 ct 3.3×3.3 mm

0.25 ct 3.5×3.5 mm

0.33 ct 3.8×3.8 mm

0.38 ct 4×4 mm

0.50 ct 4.5×4.5 mm

0.75 ct 5×5 mm

1.00 ct 5.5×5.5 mm

1.25 ct 5.8×5.8 mm

1.50 ct 6.25×6.25 mm

1.90 ct 6.75×6.75 mm

2.00 ct 7×7 mm

2.50 ct 7.5×7.5 mm

3.00 ct 8×8 mm

4.00 ct 8.5×8.5 mm

5.00 ct 9.5×9.5 mm

Radiant

0.05 ct 2.3×2 mm

0.09 ct 2.7×2.3 mm

0.15 ct 3.5×2.8 mm

0.20 ct 3.8×3 mm

0.25 ct 4×3.5 mm

0.33 ct 4.4×3.5 mm

0.40 ct 4.75×3.75 mm

0.50 ct 5×4 mm

0.75 ct 5.8×4.5 mm

1.00 ct 5.9×5 mm

Pear

0.05 ct 3×2 mm

0.11 ct 4×2.5 mm

0.14 ct 4×3 mm

0.16 ct 4.5×3 mm

0.20 ct 5×3 mm

0.25 ct 5.5×3.5 mm

0.33 ct 6×4 mm

0.50 ct 7×5 mm

0.75 ct 7.5×5.25 mm

1.00 ct 8.5×5.5 mm

1.50 ct 9.5×6.5 mm

2.00 ct 11×7 mm

3.00 ct 12.5×8 mm

4.00 ct 13.5×9 mm

5.00 ct 15×9.5 mm

Marquise

0.025 ct 2.5×1.25 mm

0.035 ct 3×1.5 mm

0.05 ct 3.5×1.75 mm

0.07 ct 3.5×2 mm

0.08 ct 4×2 mm

0.09 ct 4.25×2.25 mm

0.11 ct 4.5×2.5 mm

0.15 ct 5×2.5 mm

0.20 ct 5×3 mm

0.25 ct 6×3 mm

0.33 ct 6×3.5 mm

0.40 ct 7.5×4 mm

0.50 ct 8×4 mm

0.75 ct 9×5 mm

1.00 ct 10.5×5.5 mm

1.50 ct 11.5×6 mm

2.00 ct 12.5×6.5 mm

3.00 ct 15×7.5 mm

4.00 ct 15.5×8 mm

5.00 ct 17.5×8.5 mm

Heart

0.10 ct 2.7×3 mm

0.14 ct 3.2×3.4 mm

0.20 ct 3.7×4 mm

0.25 ct 4×4.5 mm

0.33 ct 4×4.6 mm

0.38 ct 4.2×4.8 mm

0.40 ct 4.5×5 mm

0.50 ct 5×5.5 mm

0.75 ct 5.5×6 mm

0.80 ct 5.5×6.5 mm

0.95 ct 6×6.5 mm

1.00 ct 6.5×7 mm

1.25 ct 6.5×7.5 mm

1.50 ct 7.25×8 mm

1.75 ct 7.5×8 mm

2.00 ct 7.75×8.5 mm

2.50 ct 8.5×9 mm

3.00 ct 9×9 mm

4.00 ct 10×10 mm

5.00 ct 11×11 mm

Trillion

0.05 ct 2.5×2.5 mm

0.09 ct 3×3 mm

0.12 ct 3.5×3.5 mm

0.15 ct 3.75×3.75 mm

0.18 ct 4×4 mm

0.23 ct 4.5×4.5 mm

0.33 ct 5×5 mm

0.40 ct 5.5×5.5 mm

0.50 ct 6×6 mm

0.75 ct 7×7 mm

1.00 ct 8×8 mm

1.50 ct 9×9 mm

2.00 ct 10×10 mm

3.00 ct 10.3×10.3 mm

4.00 ct 13×13 mm

5.00 ct 14.5×14.5 mm

Calculator for any round size

For a size not in the chart. This is calculated with the standard formula (diameter² × depth × 0.0061), not taken from a published chart.

Calculated size

–

Diameter: –
Points: –

Sources (checked October 2026)

Estimates for guidance; verify before production.

Interactive Melee and calibrated sizes Small diamonds are bought by millimetre, sieve and parcel weight; coloured stones for standard settings come in calibrated sizes. Look up either, see the stone and a carat of them at their real size, and check the numbers against the published charts. Open

Choose round melee diamonds or calibrated coloured stones, then a size.

Interactive Diamond size on the hand The same carat looks different on every finger. Choose a shape, a weight and a ring size: the stone is drawn at its published millimetre size on a finger of that exact width, so the proportions you see are true. Open

Choose a shape, a carat weight and a ring size; for true size, set the screen scale once.

Understand the result

Gem lab reports: what each section means

Size versus weight

Carat is a weight, not a size. Two diamonds of the same weight can look different in size depending on how deep they are cut, and every cutter's proportions differ a little. That is why published charts don't agree to the last decimal, and why this page shows the range.

For melee, buy and check by sieve size and parcel weight; the figures here are per stone and for guidance.

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