What Does CTW Mean?

what does ctw mean?

You might have seen the letters CTW stamped on diamond jewelry labels, perhaps on the inside band of a diamond ring or on the clasp of a diamond pendant necklace. Do you know what the abbreviation CTW means? The expert jewelers at Brilliance will explain what CTW means, as well as other common queries surrounding the term. Including its origin and even how to work out the total carat weight of a jewelry item.

What does CTW mean?

When talking about jewelry and diamonds, CTW stands for Carat Total Weight but is more commonly referred to as Total Carat Weight for diamonds or gemstones (like sapphires or rubies). Total Carat Weight is the sum of the weight of all the diamonds mounted in that particular jewelry piece. It is widely used by the global jewelry trade as well as recognized diamond and gemstone certifying agencies like the Gemological Institute of America as a standard measure of weight.

image of weighing scales that can be used to calculate ctw

Take, for example, a three-stone diamond engagement ring with one center diamond weighing 1.5 carats and two smaller 1-carat accent diamonds. The total carat weight, or ctw, of the engagement ring, would be 2.5 ctw. In other words, CTW is the sum of each of the individual weights of the jewelry piece’s stones.

In some pieces of jewelry, the letters CTW and a number (the total carat weight) will be stamped into a hidden part of the jewelry. This way jewelry makers can easily identify the total carat weight of a particular piece. Even without needing to unmount the stones to weigh them.

How To Calculate CTW In Diamonds

If you ever wanted to work out the total carat weight of a loose diamond or multiple diamonds, then all you need to know is that 1 carat is equal to 0.2 grams. To calculate the carats of a loose diamond, first, you weigh the stone and record its weight in grams. Then, divide that number by 0.2 and you will have the total carat weight of that diamond.

It also works in reverse. If you wanted to work out the actual weight of a diamond or of multiple diamonds, multiply the carat weight by 0.2. You’ll have the corresponding total weight in grams.

Why Do People Use CTW In Jewelry?

Marking CTW on jewelry is important because it can be difficult to determine the actual total carat weight of a diamond or diamonds once they are already mounted into jewelry pieces. This way jewelers can easily identify the CTW of a piece quickly and efficiently.

image of carob tree, where carob seeds and the term carat come from
Carob Tree – “carat” originates from the carob seed

What Does Carat Mean?

The word ‘Carat’ originates from the word ‘Ceratonia siliquia’ which is the Greek word for a simple Carob tree. Before measurement units were invented, diamond traders used to compare the weight of a diamond to Carob tree seeds. This was because each Carob seed was uniform in size and weight, weighing about 0.2 grams, making them a consistent and useful marker to measure diamonds against.

Some sources also claim that the actual word for Carat comes from Medieval French, Italian, and Arabic origin. With the word qīrāṭ which means ‘bean pod.’ This is also similar to the Greek word keration, referring to both carob seeds and the small weight.

What’s the difference between CTW, CTTW and CT?

Some jewelers may use slightly different terms when talking about diamonds, and it’s important to understand the difference between each of the terms.


CTW: This refers to the carat weight of one solo diamond: just the individual weight in carats of one, single gem.

CTTW: This can refer to the total carat weight of multiple diamonds. You’re probably familiar with ring settings, for example, that have smaller stones set around a larger, central gem.

CT/ct: This simply means carat.

Alongside the total carat weight, there might be A or G marked on the jewelry.

A: This refers to approximate carat weight. Some jewelry has this term on it to avoid having to be exact with its measurements.

G: Meaning guaranteed diamond weight. The guaranteed diamond weight is usually about 1 point under the weight that is sold. For example, a 1-carat 3 stone diamond ring with a 1.00 guaranteed diamond weight will need 1.01 CTW in diamonds.

Keep an eye out when shopping for diamond jewelry to ensure you understand exactly how much diamond you are buying! Brilliance has expert jewelers ready to help you with any questions you might have.

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