The purity of gold is measured in terms of a unit known as karat. This worldwide unit has great implication when you are buying gold. Let us understand the gold karat in somewhat detail before we go to see how it affects its weight.

The karat, as already described is a unit of purity of gold. It is important to keep this in mind. Karat measures how pure the gold is. Any gold sample will have a maximum purity of 24 karats. That means, the purest form of gold (and hence the most expensive) will be 24 karat gold. Actually speaking, this gold will have a purity of 999.99 per thousand. There will still be 0.01 per thousand by weight of impurity left in the gold, which is due to its refining process and this cannot be removed. For our understanding purpose though, we will consider that 24 karat gold is 100% pure gold.

You can consider 1 karat to represent 1/24^th of the purity of the gold. Let us understand this with examples. We know that gold is marked with some karat values. Now, if you were to find a gold ornament that had 16 karat mentioned on it, it means that this ornament has 16 parts of gold and the remaining 8 parts of some base metal with which it is mixed. So, 16 karat gold is actually 16/24 = 66.67% pure. The remaining 33.33% is the impurity. Similarly, if you take a gold sample that is of 20 karats, it means it has 20 parts of gold and the remaining 4 karats of impurity. In other words, it is 20/24 = 83.33% pure and has an impurity of 16.67%.

When you know the karat value of the gold item you are purchasing, you can directly calculate how pure that gold is. You can get gold of varieties such as 10 karat, 12 karat, 14 karat, 16 karat, 18 karat, 20 karat, 22 karat, 23 karat and 24 karat. Indeed, all karat values are made and sold. It is understandable that gold price depends on the karat value that it contains, and hence on its purity.

It is now clearer to understand how gold purity affects its weight. The answer is – gold purity does not affect its weight! This is because if a particular gold sample is impure, it will simply contain the remaining weight of another metal mixed with it. Because of that, the total weight may remain the same or may be different. You cannot predict how pure gold is just by measuring its weight. Gold purity is a percentage and it has nothing to do with the weight of the sample.

Most people who talk about karat influencing weight are actually getting confused between the karat used in gold purity measurement and the carat used in diamond weight measurement. Yes, for diamonds, carat means its weight. But for gold, it is not so. The only way to ascertain the purity of gold is through some tests such as acid kit tests and electronic kit tests, the kind of tests that Cash4Gold and other gold buying websites when evaluating the gold samples it gets from sellers across the world. Cash4Gold evaluates gold and then quotes an estimate cash value for it which helps the seller decide whether he or she wants to go ahead with the sale or not. They do not measure the gold purity with its weight, though that is helpful in determining its total pricing.