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The 4Cs of Diamonds


The carat is the diamond’s most popular feature and refers to the stone’s weight. Unlike popular beliefs, the carat doesn’t necessarily reflect the value, nor the apparent size. Size varies depending on other diamond aspects, such as cut and shape. However, larger diamonds are rarer than smaller ones, therefore are valued higher.  Use the interactive guide below to demonstrate the size in mm of different carat weights for each shape of diamond.

Size shown in MM

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  • Round
  • Princess
  • Emerald
  • Oval
  • Pear
  • Heart
  • Marquise
  • Cushion
  • Radiant

Size: 0.25ct



Diamond Carat Weight

The carat of a diamond refers to the weight of the stone, rather than the dimensions, with one carat being the equivalent of one-fifth of a gram. Units smaller than one carat are measured in points, with 100 points equal to one carat.

The carat weight of course impacts the size of the stone, but it is important to understand that two diamonds of the same carat weight can measure significantly different across the top, depending on the proportions of the cut. This surface measurement is how the diamond is viewed when set and gives the overall impression of size.

The proper diamond cut proportions allow the maximum return of light, delivering superior fire and sparkle while maximising the visible surface area. A poorly cut diamond of the same carat may carry most of that weight in the pavilion, or lower part of the stone, which will make the diamond appear smaller than its actual weight and significantly less brilliant than the well-cut equivalent.

Steven Stone Tip

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“If you would like to purchase a 1ct diamond and optimise your engagement ring budget, we recommend choosing a well-made 0.90ct round diamond which measures 6.25mm in width, the same physical size as an average 1ct diamond.”

Important Carat Weight Information

It is a common misconception that all 1ct diamonds appear the same size. This is not the case, as not the entire diamond is visible from the top down. The percentage of hidden carat weight, or “depth percentage”, determines the surface area of your diamond that is visible when set, and there are strict parameters for a well-cut stone. For example, a well-made round brilliant cut diamond of 1ct in weight should measure between 6.4mm to 6.5mm in width.

It is possible to find a 1ct diamond which measures as low as 5.9mm across, and such low dimensions would immediately indicate that the diamond is poorly made. Steven Stone deals only with the top 1% of diamonds and a stone of this quality would fail to meet our stringent standards for superlative brilliance. When comparing prices, please ensure you compare the measurements as well as the carat, in order to compare like-for-like, as poorly made diamonds are inevitably less desirable and therefore cheaper than a well-cut alternative.

If you would like to purchase a 1ct diamond but find it falls outside your engagement ring budget, we recommend choosing a well-made 0.90ct round diamond which measures 6.25mm in width, rather than settling for a poorly made 1ct stone. Choosing a beautifully proportioned diamond of 0.90ct will give the same surface area and presence as an average 1ct stone and will still possess the same sparkle, fire and brilliance as the more expensive option.

If you would like additional guidance or help in choosing the perfect diamond for an  engagement ring,  wedding ring, or any piece of diamond jewellery, please feel free to call our diamond experts on 0800 080 3535 or contact us using the form below.

Contact Us. Get in touch with one of our experts, we guarantee a reply within 5 working hours. No matter what the question we are here to help

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