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What to Know About Total Carat Weight (CTTW) for Diamonds

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CTTW for Diamond Jewelry

Buying diamonds is about balancing all the ways diamonds are graded and finding that sweet spot. You’ve no doubt heard of the four Cs (color, cut, clarity, and carat), and the one most shoppers try to maximize is carat. 

Bigger diamonds — whether part of a diamond ring, necklace, or earrings —  have special appeal but also come with a premium price, which is why it’s important to know how carats are measured on a piece of jewelry. 

That includes knowing what CTTW on a diamond means.

What Does CTTW Mean for a Diamond Ring?

You might notice the carats of a piece of jewelry labeled with the acronym “CTTW.” CTTW stands for “total carat weight” or “carat total weight” and indicates the total weight of all the diamonds in a piece of jewelry.

For a diamond ring, CTTW is the total weight of all the diamonds in the piece, which would include the center stone as well as any accents, side stones, or pave. 

When you’re shopping online for a diamond ring, it’s common to select the setting and diamond separately. For the setting, online retailers also display the CTTW of just the setting. So you’d add that number to whatever size diamond you buy. 

For example, this floating diamond engagement ring has a CTTW of 0.78.

Floating Diamond Ring

That means the six round diamonds set on the ring are about 0.13 carats each, and then you’d add the carat of the center diamond.

If you select a 1.25 carat center diamond, the CTTW is 2.03.

As another example, this double halo gala diamond engagement ring features French pave-set diamonds around a center stone.

Double Halo Gala Engagement Ring - Blue Nile

The pave-set diamonds total 0.88 carats, so a one-carat center diamond would equal a CTTW of 1.88.

CTTW vs. Carat: How Do They Differ?

Carat is a measurement of the weight of a diamond — not its size. One carat is equal to 200 grams. 

While heavier diamonds are often larger than lighter ones, that’s not always the case. So remember when a jeweler is talking about carats, they aren’t talking about size.

CTTW (also written as CTW) differs from carat in that CTTW is the added weight of every diamond, while carat is referring to only one diamond. So if a diamond has one center stone and two side stones, you’d want to know the carats of all three individually and then also the CTTW.

Or if a piece of jewelry has diamonds that are all the same size, you can learn how many carats each diamond is by dividing the CTTW by its number of diamonds. For example, this 14K rose gold diamond tennis bracelet from James Allen has a CTTW of three.

Rose Gold Diamond Tennis Bracelet

It has 64 total stones of equal size, so we know the carat of each stone is about 0.05.

On the other hand, some pieces of jewelry feature just one diamond. If you were to pair a 1.05 carat round diamond with this 1.5mm comfort fit engagement ring, which features no diamonds, the CTTW would just be 1.05.

Comfort Fit Engagement Ring

How Does it Affect the Price of a Diamond?

Knowing the difference between CTTW and carat is incredibly important when it comes to the prices of diamonds. If you don’t know the distinction, you could overpay by hundreds or thousands of dollars, because CTTW and carat significantly impact the value of a piece of jewelry. 

This is because the price of a diamond increases disproportionately as its weight increases.

Let’s take the example of three diamonds from James Allen that are the same color, cut, and clarity, but differ in carat.

You can buy a 0.50 ct diamond from James Allen for about $1,350. If we increase the diamond by 0.50 carats to make it a one-carat diamond, its price does not just double — it’s $5,000. If we add another 0.50 carats, the price goes up to $12,490.

Why is the diamond that has three times as many carats not just three times the price? Because larger diamonds are more rare, and the rate of price increase generally rises with the weight of the diamond.

If this were not the case, you would expect a 1.50 carat diamond to cost three times more than a 0.5 carat diamond, with all other qualities being equal.

This distinction is why it’s critical to understand the difference between carat and CTTW. If the CTTW of a diamond is split between two or more diamonds, that jewelry piece should cost less than if the piece only had one diamond.

And all else being equal, a piece with CTTW split between two diamonds will generally be more expensive than one with it split between three diamonds. This pattern continues the more diamonds you add to the piece, splitting up the CTTW by more diamonds.

Find the Right Carat Weight for You

There’s numerous criteria to evaluate when assessing the value of a diamond, but misunderstanding carat versus CTTW is one that could cost you the most if you get it wrong. Carat has a significant impact on price, and a key point to grasp is price relative to carat does not increase proportionately.

A diamond with double the carats doesn’t cost twice as much as its comparison.

So when examining the CTTW of a diamond, don’t expect the price to be the same for a piece where all the carats are in one diamond. Expect a piece to be cheaper if the carats are split up among more than one diamond.

It won’t be as valuable as a piece with one large diamond, but it can be the right choice for someone wanting to stay on budget.

Devon Tyler

Devon Tyler

Devon Tyler is the founder of TeachJewelry.com.

He earned an Applied Jewelry Professional Diploma from the Gemological Institute of America and now brings you essential information about diamonds, settings, and more.

Devon has consulted with leading jewelry brands, and his work has been cited in Diamond Nexus and other industry publications.

He's also a member of the International Gem Society.

Devon enjoys discussing jewelry with readers, so contact him with any questions at tyler.devon@teachjewelry.com.

Learn More About Devon