Carat

There is a misconception that carat measures the physical size of the diamond, but it is in fact a measure of the weight. It is also not to be confused with gold’s ‘Karat’, which measures the purity of gold. The quantity is as follows: 1 carat = 0.2 grams and 5 carat = 1 grams As the carat weight increases so too does the size however the two are not perfectly correlated. A 1.0ct diamond is not five times larger than a 0.2ct diamond.

Carat weight should not be looked at in isolation but along with the other 4Cs, namely ‘cut’. The visual appearance of a diamond is governed mostly by the cut. It is common to find two diamonds with the same carat weight that appear to be a different size due to the cut grade. A well-cut diamond such as ‘Very Good’ will appear larger than a ‘Fair’ cut diamond even if both have the same carat weight due to how well the diamond reflects light. Learn more about ‘cut’ here.

Diamond prices vary significantly every whole and half carat mark, and there is often a big difference in price between for example a 0.9ct and 1.0ct diamond, without a significant difference in size. Therefore a 0.9ct diamond could be significantly less in value than 1.0ct diamond.

It is also important to understand that other characteristics of diamonds which will have an impact on value other than just the size.

Here we have put together a really useful set of videos showing size comparisons and
how they would look in real life when mounted into a ring.

Diamonds Size

Carat Weight

0.25ct

0.5ct

0.75ct

1ct

1.5ct

2ct

3ct

4ct

5ct

Carat Weight

Round

4mm

5mm

5.5mm

6.5mm

7.5mm

8mm

9.4mm

10.4mm

11.2mm

Princess

3.5mm

4.5mm

5mm

5.5mm

6.8mm

7.5mm

8mm

8.9mm

9.7mm

Heart

4x4mm

5x5mm

6x6mm

6.5x6.5mm

7x7mm

8x8mm

9x9mm

10x10mm

11x11mm

Emerald

4x3mm

6x4mm

6.5x4.5mm

7x5mm

8x6mm

8.5x6.5mm

10x8mm

11x9mm

10x10mm

Asscher

3.7mm

4.4mm

5mm

5.8mm

6.4mm

7mm

8.1mm

9mm

9.6mm

Marquise

5x3mm

8x4mm

9.4.5mm

10x4.75mm

11x5mm

12x6mm

14x7mm

15x7mm

16x8mm

Radiant

3.5x3mm

5x4.5mm

5.5x5mm

6x5.5mm

7x6mm

7.5x7mm

8.5x7.5mm

9.5x8.5mm

10x9mm

Cushion

4x3.5mm

5x4.5mm

6x5mm

6.5x5.5mm

7.5x6.5mm

8x7mm

9x8mm

10x8.5mm

10x9.5mm

Oval

5x3mm

6x4mm

7x5mm

7.5x5.5mm

8.5x6.5mm

9x7mm

10x8mm

11x9mm

12x10mm

Pear

4x2mm

6x4mm

7x5mm

8x5mm

9x6mm

10x7mm

12x8mm

14x9mm

15x10mm