Most people express diamond carat weight in percentages, such as quarter carat, half carat, three quarter carat, 1-carat, and so forth. They also guesstimate the value of your ring, or how much you spent on it by what it weighs.
The reality however is that other factors such as diamond color, diamond clarity and diamond cut quality also have a significant effect upon the price of a diamond and thus it is common for smaller diamonds to cost more than larger ones.
Within the diamond industry there are several ways of expressing diamond carat weight. A one carat diamond weighs 100 points, just like there are 100 pennies in a dollar.
It is expressed in written form as 1.00 carats. The term "points” does not refer to the number of facet junctures that are created by the facet structure of a diamond.
What Is a Point of Carat Weight?
It is a representation of weight which originated in Egypt when carob seeds were used to determine the weight of a gem stone. When describing a half carat diamond weighing 0.52 carats, a store owner might refer to it as a "52 pointer” instead of saying it weighs "zero (point) five two carats)”.
In the old days, diamond wholesalers frequently referred to diamonds that weighed about one-quarter carat, or its multiples, as being so many grains. A grain roughly equals twenty five points or one-quarter carats, expressed as 0.25 carats. A 0.74 carat diamond, for example, would be referred to as a three-grainer.
A 1.25 carat diamond would be called a five grainer and so on, today the stone would be described as "a carat twenty five” or a "carat and a quarter” but a few of the old timers still talk amongst themselves in terms of grains just to see if us young pups are up to speed.
Keeping It Legal:
The Federal Trade Commission has set forth guidelines concerning the proper representation of carat weight to the public. The diamond's actual weight must fall within two points (0.02 carats) of the fractional representation.
For instance, a diamond represented as weighing one-carat should fall within a range of 0.98 to 1.02 carats. A half-carat diamond should weigh between 0.48 and 0.52 carats, and so on.
A diamond weighing 0.72 carats should not be represented by a person within the industry as being a three-quarter carat. Although 0.72 carats is barely shy of the magic mark, it's still not considered a three-quarter carat diamond.
The fact of the matter is that your significant other can call her sixty-eight pointer a three-quarter carat, and her girlfriends will just have to take her word for it... We, on the other hand, can't get away with that and have to express the weight of the diamond in correct legal terms.
Truth in Advertising Diamond Carat Weight:
When buying diamond jewelry advertised as having "a carat total weight" you should make sure that you're getting what you pay for.
For example, a pair of one-carat total weight diamond earrings, or a one-carat total weight cluster style ring should have a combined total diamond weight that falls somewhere between 0.98 and 1.02 carats.
If the combined total weight is actually 0.85 carats, then you're not buying a carat total weight and you should realize the difference. On the other hand, if the one-carat total weight diamond ring that you're looking at actually contains a total weight of 1.10 carats then the other eight points are a bonus for you and you should consider yourself lucky.
We frequently see advertisements that describe diamonds in fractional terms such as (one quarter carat, half carat, etc.) and wonder whether the actual weight of the diamonds fall within the legal guidelines.
Don't be afraid to ask the sales clerk what the actual weight of the diamonds contained in the piece of jewelry is. Your jeweler should be happy to provide you with the item's actual diamond weight and will be impressed with the fact that you knew enough to ask.
Diamond Carat Weight Size Reference Chart:
Be sure to download this carat weight size reference chart from Blue Nile. After all, it's easier for most people to visualize carat weight than to imagine what millimeter sizes look like.
This chart will help you see how big round and fancy shape diamonds look depending on carat weight. It includes size references for round, princess, emerald, Asscher, marquise, oval, radiant, pear, heart, and cushion cut diamonds.
At the same time, it's important to remember that this is a general guideline. The actual size of your diamond will vary depending on the proportions. With that in mind, be sure to read our tutorial on calculating diamond proportions.
It is also possible to estimate the carat weight of a mounted diamond by formula. That is something you might see if you take your ring to a gemologist for an appraisal.
Have a Little Fun Explaining Diamond Carat Weight:
Regardless of what you’ve been told by those who might want to spare your feelings, sooner or later it all boils down to size.
No matter how beautiful the diamond is, some schmuck (like her dried up, old spinster of an Aunt) is going to Pin the Tail on the Donkey in front of the whole family and ask:
"So we’re all dying to know, uh, what’s his name? Uh Melvin, Shmelvin, uh whatever, Kevin, that’s it, Kevin! Anyway, so how BIG is it?”
Word of advice. She’s probably referring to the diamond.
Fatal, although possibly appropriate, responses to questions pertaining to the size of the diamond:
"It’s not the size, it’s how you mount it.”
"Bigger is not always better”
— Emphasized by staring at Auntie Spinster’s backside & shuddering.
"I went for quality, which apparently was not available back in your day.”
— Take a moment to squint at the Aunt’s never used, self purchased, promise ring and mumble something about needing to remember to get your eyes checked.
"Bigger than the hairy mole on your chin, but not as big as your…”
— Again, you have to physically shudder for this to work.
It's All Fun and Games Until Somebody Gets Their Carats in a Bunch:
Ah yes, we digress, but no more or less than we would if we were sitting around discussing this subject in person. By now you’ve probably figured out that this is not your usual glossy version of the 4C’s outlined on those average jewelry store pamphlets. The truth is that we’re actually going to teach you something and using humor makes it more fun and memorable.
While we admit that the responses indicated above are probably accurate and possibly appropriate, they are not likely to make the transition into your new family easier. Therefore we advise strongly that you refrain from speaking your mind, regardless of the insight provided on this web site.
If ignorance is bliss, then let the ignorant be, well, ignorant. The old bat really doesn’t deserve a response, but in an effort to maintain peace between opposing forces, we’ve crafted the following "more appropriate” excuses for not producing the Hope Diamond to Wow & Amaze the family.
"About a Bushel."
Say this with total conviction because it is an absolutely viable explanation: Diamond carat weight was originally measured using carob seeds as a comparison of weight with 100 carob seeds equaling one carat.
Each carob seed is referred to as a "point" so a diamond weighing 1.49 carats which is commonly referred to as "a carat and a half" is accurately represented as "149 points" which is equivalent to 149 carob seeds and that my friends sure sounds like "about a bushel" of carob seeds to me.
"I don't know, but I liked that balance between it and the mounting."
This is a rather easy explanation to defend because it is all a matter of personal preference and perception. If the Spinster Aunt happens to say something along the lines of "well, the diamond doesn't look large enough to me" you can say something about being able to upgrade to a larger diamond as you both get older and it becomes more difficult to see things without a magnifying glass.
Be sincere and polite, remember it's never nice to be rude to your elders. You're not implying that the Aunt can't see, you're just explaining the benefits of buying a diamond from a dealer with a great upgrade policy!
If you really want to have fun with this and boggle their minds, then you can talk about how AGS Advanced ASET uses ASET-30 and ASET-40 hemispheres to show the difference in how diamonds reflect light from close-up and far away. In addition, ASET-30 is likely to represent how we will see the contrast brilliance within the diamond when we are younger and ASET-40 demonstrates how it will look when we are older.
And you thought that I was just making fun of Ol' Auntie Spinster because she's an old spinster. Shame on you!
"It Averages 6.5 mm in Diameter."
This is a kick because only a techno-geek will know that the average outside diameter of a 1.00 carat round shape diamond averages 6.5 mm. The family will hear 6.5 and spend the rest of the evening thinking that you were referring to the carat weight and second guessing the size of their diamond.
If it's a princess cut diamond, give them the tip-to-tip measurement as measured diagonally across the diamond because it sounds even more impressive. Since diamonds come in all shapes and sizes, refer to the measurements section on the diamond grading report for the dimensions in millimeters.
By the way, the average diameter of the pink eraser on a standard #2 yellow pencil is also 6.5 mm in diameter. The funny thing about this is that I know that you're going to pull that little piece of trivia out of your hat as soon as the opportunity presents itself. Rest assured that I'm laughing with you and not at you. Consider the source.