Carat (ct) & Karat (kt) – what’s the difference ?

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Carat (ct) and Karat (kt) – what’s the difference ?

This is a source of confusion for many buyers as the pronunciation of the words is the same but in reality they are very different

Carat is the weight of a stone

One Carat of weight is 0.200g of mass (weight) = 0.0070548 oz

Since the Heavier the stone the larger the stone the following details the approximate diameters of a Round Brilliant Cut Diamond – note this is true only for diamonds, since other stones have different density & therefore the sizes will vary from this table in accordance with the density of the type of stone.

2mm – 0.03 Carat
3mm – 0.10 Carat
4mm – 0.23 Carat
5mm – 0.47 Carat
6mm – 0.80 Carat
6.5mm – 1.00 Carat
7mm – 1.25 Carat
8mm – 1.90 Carat
9mm – 2.50 Carat
10mm – 3.50 Carat
11mm – 5.00 Carat

Most engagement rings are in the range 4-7mm (that is 0.23-1.25 Carats), while anything over 7mm (1.25 Carats) is very large & anything over 9mm (2.50 Carats) is really huge !!! & diamonds of this large size are rarely seen.

Karat is the percentage of Gold in a piece of metal expressed in fraction of 24th’s

For example 10 Karat means 10/24 Gold = 41.7%

The following table details the percentage of pure gold in each of the commonly available “Karats” that jewellery is usually available in:

9 Carat = 37.5%
10 Carat = 41.7%
12 Carat = 50.0%
14 Carat = 58.3%
18 Carat = 75.0%
20 Carat = 83.3%
21 Carat = 87.5%
22 Carat = 91.7%
24 Carat = 100.0%

Because Gold is coloured the higher the Karat the more gold there is & therefore the darker yellow the gold.

Many Asian Jewelers add Copper to the Gold to make it appear very dark yellow while Western jewelers traditionally add non coloured metals to the gold to make it harder & less likely to wear over time. This is why you see a great colour difference between some similar pieces of jewellery that have the same Karat rating.

So the diamond ring you buy will have a weight of the stone measured in Carats & it will also have a purity of the gold in the ring measured in Karats -it will always have both !!!




We have a range of items at NRS-Diamonds from SI1 to I4 & are constantly updating our stocks (

And just in case you’re not happy with your purchase we offer refunds as detailed in our eBay advertising & we’re always happy to provide advise.

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