This article ("The value (quality) of a diamond is determined by the '4Cs'") as introduced in the article, 1 carat (ct) = 0.2gWeightIt is not an index of size, so even if the carat weight is the same, the apparent size may vary slightly. This unit is also used for all gemstones, including rubies and sapphires, in addition to diamonds. Different gemstones have different specific gravities, so even if they weigh 1 carat, the apparent size of a 1 carat diamond will vary from that of a 1 carat ruby. Also, even the same ruby ​​will have different depths, so even if they have the same shape and the same carat weight, their apparent size will differ. For this reason, when comparing colored stones, actual dimensions are often used.

When comparing diamonds, if the cut standard is excellent, the size difference will not be that great. Please refer to the table below for approximate sizes of round brilliant cut diamonds.
A difference of 0.1ct will only change the diameter by about 0.4 to 0.7mm, but the difference is immediately noticeable when comparing. If it is about 0.05ct, you won't be able to tell the difference unless you look closely.If you want something a little larger, choose a stone that is about 0.1ct larger. If you want something a little smaller, choose a stone that is about 0.1ct smaller..

The preferred carat size has changed depending on the culture of the country and the times. Of course, it depends on the individual, but Japanese women tend to choose small, high-quality diamonds of around 0.3 carats. However, during the bubble era, diamonds of around 1 carat were preferred, even if it meant lower quality. If the economy improves from now on, carat sizes may also increase.
But what about overseas? This is just a rule of thumb, but people generally prioritize carat weight and tend to choose larger diamonds. Overseas customers who visit our store are generally looking for diamonds over 1 carat. Japanese customers living overseas also tend to choose larger diamonds. This is a reflection of Japan's unique culture.

Do you know the origin of the word "carat"? The word "carat" comes from the seed of the carob (locust bean). Carob seeds are very uniform, weighing approximately 0.2g. In the past, jewelers used carob as a counterweight on their scales to measure gemstones and other items. Later, in 1913, the United States adopted the metric carat system (unit: ct), and carat became the international standard.
Also, there are many appraisal agencies around the world, and each agency displays the carat weight differently.
GIA, the international standard for value, displays the value to two decimal places, such as 1.00ct, but Japan's largest Central Gem Laboratory (CGL) displays the value to three decimal places, such as 1.000ct.
At Hojudo, we handle both types of diamonds, but we have more GIA certified diamonds in stock.
For more information about GIA, please refer to the following pages:

▼What is a GIA certified diamond?

When it comes to engagement rings, the most commonly chosen carat weight is around 0.3 carats. Many Japanese customers prioritize smaller sizes and quality. However, at Hojudo, prices are reasonable, so many customers choose rings around 0.4 carats.
0.5ct is generally considered large, but 1ct has a strong presence and you can see its size even from a distance.
If you aspire to a 1ct diamond and are particular about size, then you should think of it as 1ct or more; if you like flashy, large accessories, then you should think of 0.5ct or more; and if you don't want it to stand out too much, then you should think of 0.3ct.

Some young customers in their teens and twenties who want to wear it casually as an accessory for everyday use choose 0.1-0.2 carat diamonds, but as they get older, they tend to choose larger carats. Customers in their 40s and older often prefer 0.5 carats or more. Therefore, if you are purchasing a diamond to last a lifetime, it is best to choose a slightly larger diamond. At Hojudo, the number of customers choosing 0.2 carats is significantly lower than with other brands.

The appropriate carat number will also vary depending on your height and finger size.
It's best to try it on before deciding, but if you're tall or have long fingers or larger fingers, choose a larger carat number. Conversely, if you're petite and have smaller fingers, you may want to choose a slightly smaller ring.

When you try on a diamond ring for the first time, the diamond may seem large, but strangely enough, you soon get used to it. Therefore, if you decide on a smaller diamond right away, you will likely regret it, so try on several rings and take your time to choose.
(Some customers who have seen a 0.2ct diamond at another store and then seen a 0.4ct diamond at Hojudo are hesitant, thinking it is too big, but after trying on a few more, they often end up ordering a 0.4ct diamond and are very satisfied.)

It also depends on the design. A halo design, where the center diamond is surrounded by small diamonds, will add volume.Therefore, even relatively small diamonds will appear larger. The balance with the ring design, such as the thickness of the arms, is also important.

Since rings are often viewed up close, many customers choose smaller diamonds that emphasize quality, but when it comes to pendant necklaces, many people choose larger diamonds over quality.Generally speaking, if you want to wear it every day, we recommend 0.3ct, but if you want to wear it for the rest of your life, we recommend 0.5ct or more. As with rings, many people increase the carat size as they get older.Additionally, some people who don't normally wear rings choose pendant necklaces instead of engagement rings. When it comes to engagement necklaces, many people are particular about both size and quality, and many of our customers choose pendant necklaces with a carat weight of 0.3 to 0.4 carats.
As with rings, the key points to consider when choosing a ring will depend on your preferences and body type. If you are tall or have a fuller figure, it is best to choose a larger carat number, and if you are petite, a smaller carat number is best.


If the design is a halo, it will have volume, so even if you choose a relatively small diamond it will look large, so be sure to choose one that is balanced.

Also, if you feel that the diamond in the prong ring inherited from your mother or grandmother is a little too big, we recommend having it remodeled into a pendant. It's less expensive, and pendants are easier to wear, so they can be worn in a wider variety of situations. Hojudo is also good at remodeling. Please refer to the detailed explanation on the page below.

▼For those renovating for the first time

Like necklaces, earrings are rarely seen up close, so many customers place more importance on carat weight than quality.However, people tend to choose smaller diamonds than necklaces.If you have a 0.5ct pendant and 0.5ct earrings, the appearance will be quite different, and the 0.5ct earrings will look much larger.
Some people choose smaller diamonds of around 0.1ct for everyday use, but at Hojudo, diamonds in the 0.2ct or 0.3ct range are often chosen.
Considering that it will be used for a long time, it is best to choose one that is 0.3ct or larger.
This also depends on your preference, body type, and earlobe size, but if you usually wear large earrings or have large earlobes, you should choose a slightly larger diamond, but if you have small earlobes and want to keep a more subtle look, you should choose a slightly smaller one.



In the case of earrings, a 0.1ct difference can have a much bigger impact on the look than a ring or pendant. We recommend trying them on first to see which size you'll choose.
If you would like to know more or compare diamonds in person, please feel free to contact us or visit our store.