Diamond Carat Weight

Carat Weight (one of the 4C’s) is simply the Weight of a Diamond, be it One Carat or a Half Carat. It’s all about how much the Diamond Weighs.

Back in the days, Diamonds were weighed by seeds from a Carob Tree (where the word Carat comes from). These seeds were roughly the Weight of one Point (1 pt) to a Diamond. Since there are 100 Points in a Full Carat Diamond, there would be 100 Carob Seeds to balance it on a Scale.

But, as we all know, things grown in nature are never quite perfect (just like Diamonds, just like people). Weighing Diamonds with seeds was never an exact science.

The Diamond Scale

Things were never exact until the Diamond Scale was invented in the early twentieth century. Now, getting the exact Carat Weight of a Diamond is easy and only takes a couple of seconds.

But, no matter how easy it is to find the Carat Weight, people still have a hard time understanding it.

Decimals, Fractions, Points, Carats, Math… Can’t they make it anymore difficult?

It all Boils down to Money!

Carat Weights and Points are not that hard to comprehend when you know the little secret. Treat Carats and Points like Dollars and Pennies. Really! If you can count money, you already know Carat Weights.

  • One Dollar = 100 Pennies, right?
  • 25 Pennies gives you a Quarter, or 1/4 of a Dollar.
  • 50 Pennies would be 1/2 or 50 Cents…

But how do Carats fit in?

The same way!

  • There are 100 Points in a One Carat Diamond (written as 1.00 Carat). So 1/2 Carat Diamond would simply be 50 Points or .50 Carat.
  • A 1/4 Carat Diamond would be 25 Points (.25 Carat).
  • 3/4 Carat (.75 Carat) would be 75 Points. Are you following this? It really is that easy.
  • A 10 Point Diamond is 1/10 of a Carat or 10 Points.
  • A 1.50 Carat Diamond is One Carat and a Half, or a Carat and 50 Points (150 Points in all).
  • So then when you see a .38 Carat Diamond, you’ll know it’s a little more than 1/3 Carat (.33 CT) and a little less than a Half Carat (.50 CT).
  • 58 Points is in between 1/2 and 3/4 (.50 CT & .75 CT).

So when a Jeweler tells you that the center Diamond of an Engagement Ring is 89 Points (.89 Carat), you’ll know that it’s just 11 Points shy of being One Full Carat (1.00 Carat).

Take a look at the image below to see all the different sizes of Carat Weights!

Carat Weight Chart

Carat Weight Millimeter Sizes

The Standard Millimeter (mm) sizes of Diamond Carat Weights are as follows:

Standard Diamond Carat Weights

Points – Carats – Fractions

Take a look at the chart below to see what the Points are, Carats are and Fractions are of your Diamond. Plus, see what that Carat Weight is often referred to as.

Diamond Carat Weight Points Carats Fractions Chart

The Dream Carat Weight

If you’ve been looking at Diamonds, especially Diamond Engagement Rings, you’ll know that a One Carat Diamond is the Dream Diamond. That’s the size that every woman wants (or at least 99.9% of them).

One Carat Diamonds are the cream of the crop. The show stopper! It’s the perfect size for any Diamond Ring and the perfect size for any finger.

But sadly, One Carat Diamonds are large and quite expensive. That’s why the average size for a Diamond Engagement Ring is only 38 pts. So don’t fret it, average works out to be pretty affordable to all! :)

Carat Weight and Carat Weight Total

One thing to note here about Carat Weights is that there are different types of Carat Weights that shouldn’t be confused.

If you’re looking at a Diamond Solitaire (Single Diamond), then the Carat Weight is simple; it’s the Weight of that single Diamond.

But, if you’re looking at a Diamond Wedding Set, then things can change dramatically. You’ll have the Carat Weight of the center Diamond AND the Carat Weight of the side stones.

A lot of times Jewelers will refer to the Carat Weight of the entire ring when you are asking what the Carat Weight is. They’ll say something like “The Carat Weight of this ring is 1.25 Carats“. This may sound really good, but when you compare Diamond Rings elsewhere of 1.25 Carats you’ll see that the price is WAY different… All for a very good reason…

The Jeweler was giving you the Total Carat Weight of the ENTIRE ring (or Carat Total Weight written as ctw), and not the breakdown of the Center Diamond Carat Weight and the side stone Carat Weight. This makes a HUGE difference.

The center Diamond could only be .33 Carat and the other .92 Carat could be in the little side Diamonds. Not good! Especially if the ring down the street had a much larger Carat Weight in the center.

The point is, if they give you a Carat Weight of the ring, make sure you find out if that’s the Carat Weight of the center Diamond or the Carat Weight of the entire ring. Knowing this info can help you compare rings and prices elsewhere. Otherwise you could really be taken!

The Same Carat Weights can look different!

Two One Carat Diamonds put side by side can also look totally different in size as well. It’s like two people standing side by side could be the same weight, but one could be tall and skinny, the other short and fat. Diamonds are no different. From the top view, one could look 25% smaller than the other Diamond, if not more. It all depends on how the Diamond is Cut (which all depends on how much profit they can make from the initial parent rock).

In Carat Weights, you have to look at everything to understand what’s really going on. Things like mm sizes, Ideal Proportions and Girdle Thickness all come into play (which we will all get into with other posts).

Everything is affected by Carat Weight, even the Inclusions in the stone (or more appropriately, the Clarity of the Diamond). Carat Weight affects how strictly Diamonds are graded as well. Bigger Diamonds get graded more thoroughly.

Larger Carat Weights make it easier to spot Flaws and Imperfections, plus larger Carat Weights also show off the Color of the Diamond better.

All Good Things to Consider with Carat Weights…

We will get to all this, but for now, it’s time for the next C of the 4C’s:

Diamond 4Cs Guide Diamond 4Cs Cut Guide Diamond 4Cs Color Guide Diamond 4Cs Clarity Guide


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  1. Thank you that was so help full

  2. Thank you you taught me few things I did not know before

  3. I have a 10 point diamond sitting inside a 18 ct gold ring
    Just need to know what it’s closest worth us to sell it
    And one valuer said it was just below there threshold to buy it
    I’m confused as to what that means if u know pls tell me

    • Hi Lamiya. I can’t tell you from the information you supplied. You would have to get a value from someone who could physically look at the ring, the quality of the stone, measure it, get the weight of the gold, the condition… All to get some kind of a value, which is usually about 20-30% of what you paid for it. -Richard

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