Professional Old European Diamond Size Chart

Detailed Old European Cut Size Comparison From CT to MM / MM to CT by Gemologists

In need of a quick and reliable way to know what an Old European cut’s ct to mm or vice versa? Curious about the deal proportions that unlock the romantic fire and vintage charm this historic cut is famous for? This comprehensive guide delivers both and more.

The Old European cut diamond is one of the most romantic and historically significant diamond cuts in the world. Developed in Europe, the cut had its most popular reign around 1890 to 1930, it features 58 facets with a small table, high crown, and deep pavilion.

These proportions were designed to maximize fire and scintillation under the soft light of candles and gas lamps. The result is a warm, romantic sparkle with larger flashes of color that feels distinctly different from the bright white brilliance of modern round brilliant cuts. The Old European cut is the direct predecessor to today’s round brilliant and remains highly prized for antique and vintage jewelry.

Below you will find a gemologically researched carat to millimeter conversion charts along with clear, practical recommendations on depth, table, girdle, culet, and length to width ratios.

Old European Cut Diamond Conversion Tool From CT to MM / MM to CT

0.25 - 5.00 cts.

OLD EUROPEAN CUT DIAMOND CARAT WEIGHT	OLD EUROPEAN CUT DIAMOND MM SIZE
0.25	3.81 - 4.06 mm.
0.3	4.06 - 4.31 mm.
0.4	4.48 - 4.73 mm.
0.5	4.84 - 5.09 mm.
0.6	5.15 - 5.40 mm.
0.7	5.42 - 5.67 mm.
0.8	5.68 - 5.93 mm.
0.9	5.91 - 6.16 mm.
1	6.15 - 6.40 mm.
1.2	6.52 - 6.77 mm.
1.3	6.70 - 6.95 mm.
1.4	6.87 - 7.12 mm.
1.5	7.03 - 7.28 mm.
1.6	7.19 - 7.44 mm.
1.7	7.33 - 7.58 mm.
1.8	7.48 - 7.73 mm.
1.9	7.62 - 7.87 mm.
2	7.75 - 8.00 mm.
2.2	8.00 - 8.25 mm.
2.5	8.36 - 8.61 mm.
2.7	8.58 - 8.83 mm.
3	8.89 - 9.14 mm.
3.5	9.36 - 9.61 mm.
4	9.80 - 10.05 mm.
4.5	10.19 - 10.44 mm.
5	10.56 - 10.81 mm.

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What Does an Old European Cut Diamond Look Like on Hand?

An Old European cut diamond displays its romantic vintage charm beautifully once placed on the finger. The classic round shape with a smaller table and higher crown gives it a unique domed profile that feels substantial and full of character.

The Old European Cut provides a uniquely different experience than the crisp white sparkle of modern rounds.

This antique cut produces soft, warm flashes of colored fire that dance gently with hand movement, the kind of glow that was perfectly suited to candle and gas lamp lighting. Many people love how it offers a soulful, heirloom quality that feels both elegant and nostalgic in real life.

If you’ve ever wondered what an Old European Cut Diamond would look like when worn and how it changes visually based on the carat weight, the on hand size guide below should be of great help.

What are the Ideal Proportions of an Old European Cut?

The Old European cut is an antique brilliant style cut that demands specific proportions to achieve its signature warm fire and romantic appearance. Due to its small table, high crown, and larger culet, the first thing that you’ll notice is how different its ideal measurements are when compared something like a brilliant round cut.

What is the Ideal Diamond Depth and Table for the Old European Cut?

Old European Cut Diamond Recommended Proportions Guide

Achieving the right balance of depth and table percentage is essential for an Old European cut to display the desired dispersion and the vintage charm it embodies, all while ensuring it doesn’t start appearing too dark or overly bright. Through research and gemological expertise in antique cut diamonds, the following ratios are what has the best success rate of ensuring the stone shows off its classic beauty and impressive face up size.

	EXCELLENT	VERY GOOD	GOOD
Table - %	48% – 55%	46% – 58%	43%– 62%
Depth - %	62% – 69%	59% – 72%	57%– 75%
Girdle	Thin to Slightly Thick	Very Thin to Thick	Very Thin to Very Thick
Culet	Medium to Large	Small to Very Large	None to Very Large

What is the Ideal Old European Shape Diamond Length to Width Ratio?

Because the Old European cut is a round shape, the length to width ratio is one of the most important factors for maintaining a pleasing circular outline. The ideal ratio is very close to 1.00. While personal taste vary, the ratios below have consistently proven to deliver the most balanced, elegant, and desirable round appearance that sets a quality Old European cut apart from every other shape.

	EXCELLENT	VERY GOOD	GOOD
Length To Width Ratio	1.00 – 1.05	0.98 – 1.08	0.95 – 1.12