There are many things to check when approaching to buy a diamond or a diamond engagement ring. But, usually, when you are about to make the step the two first questions that come to mind are:

  1. How much does it cost?
  2. How many carats is it?

As for the first one - we "happened" to have an article that explains all there is to know about how the price of diamonds is calculated.

As for the second question - how many carats is that diamond? (or in other words “how big is it?) - you’ve come to the right place!

In this article you’ll find everything starting from what is a carat, deeper look into carat vs size and I’ve also included quite a few tips that will help you save a lot of money. So feel free to jump between the section or if you have about 4 minutes - reading it all will get you all of the information you need.


What is a Carat?
How do You Tell How Many Carats a Diamond Is?
Diamond Carat vs Diamond Size
How Carat Weight affects Diamond’s Price?

What is a Carat? - The Definition

By definition, carat is a weight measurement. Just like KG, LBS. But unlike the others, it is used strictly to show the weight of gems. Any gems - from diamonds to emeralds and sapphires. The term carat comes from carob as they were believed to be consistent and accurate. 5 carobs which are equal to 5 carats weigh 1 gram. Alternatively, 1 carat equals 200 milligrams. When diamonds weigh less than a carat, it is common to use the term “points”. Every point equals one hundredth of a carat.

And when you think about it, it certainly does put things into a certain proportion - knowing that even a HUGE 5 carat diamond is equivalent simply to 1 gram.

Over the years we learned that carobs are not 100% alike but obviously with today’s technology it doesn’t really matter.

A short important note - don’t confuse carat with karat. While carat is used to measure weight, karat is used to show the percentage of gold in a ring.

Search Diamonds by Carat Weight

How do You Tell How Many Carats a Diamond Is?

Well, in continuous to the above, today each diamanter or a jewelry store owner has a diamond scale in the store. Diamond carat is measured up to two digits after the decimal point and the carats are truncated down.

Meaning that if the diamond scale shows 0.999 then the diamond’s registered carat weight will be 0.99 carats (or 99 points).

Please note that measuring the weight of a mounted diamond is practically impossible.

An estimate can be made if you know the grams of gold of the ring and then deduct it from the total weight (translating every 1 grams of gold to 5 carats). Another way is by measuring the diamond’s height and diameter but you’d be able to do so only in certain mountings and it will get you very rough general estimation (and should be done only in round diamonds)

Diamond Carat vs Diamond Size

So you want to buy a diamond! A big one… So you are looking to buy the one that weighs the most. BUT…

People tend to think that a diamond with more carats is bigger than a diamond with less. In other words that a 1 carat diamond is bigger than 0.95 carat diamond.

And in fact, if you check the GIA’s website you’d see the following definition:

“Diamond Carat Weight Measures a Diamond’s Apparent Size”

But weight does not equal size and therefore diamond carat weight does not equal to diamond size. Just like in people. A 6 foot person doesn’t necessarily weigh more than a 5’9 person…

If you are buying a GIA certified diamond, then aside for the diamond’s carat weight you’ll have the diamond’s measurements in mm. True, if you compare two diamonds that ideal cut round brilliants then the סטייה be very small but considering the impact of diamond’s weight on price - accuracy is of the essence.

How Carat Weight affects Diamond’s Price

While in the store you may see a price for the ring or a price for the diamond, originally diamonds are priced per carat. This means that if you are looking at a 2 carat diamond that costs $10,000, the diamond costs $5,000 per carat. And on the same note, if you are looking at a 0.50 carat diamond (half a carat) that costs $2,000 – it means that its price is $4,000 per carat.

But who cares and why it matters? At the end of the day you are buying a diamond… Well - it matters.

Diamonds are indeed priced per carat but the price per carat increases as the diamond’s carat weight increases. So the result is that the price of a bigger diamond (sorry - meant heavier) grows exponentially rather than linearly.