Professional Brilliant Round Cut Diamond Carat MM Conversion

MM to CT Round Cut Size Comparison Tool
Brilliant Round Cut Diamond Carat MM: 0.21 – 5.20 cts
ROUND CUT CARAT WEIGHT ROUND CUT MM SIZE
0.21 - 0.22 ct3.80 - 3.90 mm
0.23 - 0.24 ct3.90 - 4.00 mm
0.25 - 0.26 ct4.00 - 4.10 mm
0.26 - 0.27 ct4.10 - 4.20 mm
0.27 - 0.28 ct4.20 - 4.30 mm
0.30 - 0.36 ct4.40 - 4.50 mm
0.40 - 0.45 ct4.60 - 4.70 mm
0.46 - 0.48 ct4.90 - 5.00 mm
0.50 - 0.57 ct5.10 - 5.30 mm
0.60 - 0.67 ct5.40 - 5.60 mm
0.70 - 0.77 ct5.70 - 5.90 mm
0.80 - 0.85 ct6.00 - 6.10 mm
0.90 - 0.95 ct6.20 - 6.30 mm
1.00 - 1.10 ct6.40 - 6.60 mm
1.22 - 1.26 ct6.70 - 6.80 mm
1.28 - 1.30 ct6.90 - 7.10 mm
1.50 - 1.55 ct7.20 - 7.40 mm
1.67 - 1.80 ct7.50 - 7.90 mm
2.00 - 2.10 ct8.10 - 8.30 mm
2.40 - 2.60 ct8.50 - 8.80 mm
2.70 - 2.80 ct8.90 - 9.10 mm
3.00 - 3.10 ct9.20 - 9.40 mm
3.30 - 3.40 ct9.50 - 9.60 mm
3.50 - 3.70 ct9.70 - 9.80 mm
3.80 - 3.90 ct9.90 - 10.00 mm
4.00 - 4.10 ct10.10 - 10.20 mm
4.30 - 4.40 ct10.30 - 10.50 mm
4.50 - 4.60 ct10.60 - 10.70 mm
4.70 - 4.80 ct10.80 - 10.90 mm
4.90 - 4.99 ct10.90 - 11.00 mm
5.00 - 5.20 ct11.10 - 11.20 mm

Round Cut Melee Diamond Conversion Chart (0.005 – 0.20 cts)

ROUND CUT CARAT WEIGHT ROUND CUT MM SIZE CTS/PCS ROUND CUT SIEVE SIZES
0.005 ct0.90-1.10 mm1/200+000/-0
0.006 ct1.10-1.15 mm1/175+0/-1
0.007 ct1.15-1.20 mm1/150+1/-1.5
0.008 ct1.20-1.25 mm1/120+1.5/-2
0.009 ct1.25-1.30 mm1/100+2/-2.5
0.01 ct1.30-1.35 mm1/100+2.5/-3
0.011 ct1.35-1.40 mm1/100+3/-3.5
0.012 ct1.40-1.45 mm1/80+3.5/-4
0.013 ct1.45-1.50 mm1/80+4/-4.5
0.014 ct1.50-1.55 mm1/70+4.5/-5
0.016 ct1.55-1.60 mm1/60+5/-5.5
0.018 ct1.60-1.70 mm1/50+5.5/-6
0.021 ct1.70-1.80 mm1/50+6/-6.5
0.025 ct1.80-1.90 mm1/40+6.5/-7
0.029 ct1.90-2.00 mm1/30+7/-7.5
0.035 ct2.00-2.10 mm1/30+7.5/-8
0.039 ct2.10-2.20 mm1/25+8/-8.5
0.044 ct2.20-2.30 mm1/25+8.5/-9
0.052 ct2.30-2.40 mm1/20+9/-9.5
0.058 ct2.40-2.50 mm1/20+9.5/-10
0.069 ct2.50-2.60 mm1/15+10/-10.5
0.074 ct2.60-2.70 mm1/15+10.5/-11
0.078 ct2.70-2.80 mm1/12+11/-11.5
0.086 ct2.80-2.90 mm1/12+11.5/-12
0.095 ct2.90-3.00 mm1/10+12/-12.5
0.108 ct3.00-3.10 mm1/10+12.5/-13
0.116 ct3.10-3.20 mm1/8+13/-13.5
0.13 ct3.20-3.30 mm1/8+13.5/-14
0.145 ct3.30-3.40 mm1/6+14/-14.5
0.155 ct3.40-3.50 mm1/6+14.5/-15
0.165 ct3.50-3.60 mm1/6+15/-15.5
0.19 ct3.60-3.70 mm1/5+15.5/-15.75
0.20 ct3.70-3.80 mm1/5+15.75/-16.5
NGD Diamonds – Contact us for any specific size requirement

Ideal Proportions for Round Brilliant Cut Diamonds

ParameterExcellentVery GoodGood
Table (%)53% - 58%52%-53% or 58%-60%51% or 61%-64%
Depth (%)59% - 62.3%58%-58.9% or 62.4%-63.5%57.5%-57.9% or 63.6%-64.1%
Crown Angle34 - 34.932.1-33.9 or 35-35.930.1-32 or 36-37.9
Pavilion Depth (%)42.8% - 43.2%42%-42.7% or 43.3%-43.9%41%-41.9% or 44%-45.5%
GirdleThin to Sl. ThickVery Thin to Sl. ThickVery Thin to Thick
CuletNoneVery SmallSmall

What is the Ideal Brilliant Round Cut Diamond Length to Width Ratio?

Category Length to Width Ratio
Excellent / Very Good 0.99 - 1.01
Good 0.98 - 1.01