What does a one carat diamond actually cost. This article works through the market range for a one carat lab grown diamond, how that price is formed, and the prices ANNA DIAMOND actually sells at. The answer first. Jewelry set with a single one carat stone starts at 385,000 JPY, and pieces totaling one carat start at 198,000 JPY, tax included, as of August 2026.
- How large one carat is
- The market range at one carat, next to mined
- One carat in a single stone and one carat in total are different things
- The three things that set the price
- A one carat that is too cheap has a reason
- The one carat prices at ANNA DIAMOND
- Frequently asked questions
How large one carat is
Carat is a unit of weight, not of size. One carat is exactly 0.2 grams. In the round brilliant cut, which is the most common, the diameter seen from above comes to about 6.5mm.
As a figure it can sound small, yet on a fingertip or at the neckline it carries a clear presence. One carat became a marker in jewelry because of that brilliance anyone can see, and because of the price that came with it. Lab grown diamonds have lowered that threshold considerably. For lab grown diamonds themselves, What is a lab grown diamond covers the ground from the beginning.
The market range at one carat, next to mined
A lab grown diamond and a mined diamond are the same stone in chemical composition, in hardness and in brilliance. What differs is where they are born, and what they cost. With that said, here are the two at one carat, side by side.
ONE CARAT JEWELRY, TYPICAL SELLING PRICES
Mined diamond
the usual level for an engagement ring
From about USD 6,300
Lab grown diamond
the ANNA DIAMOND selling price
From about USD 2,400
Compared on the same quality standard of F color and above, VS clarity and above and Excellent cut, that is around a third. Converted at about 159 JPY to the dollar in August 2026, so the figures move with the rate. Prices on our product pages are shown in Japanese yen.
To compare like for like, in the quality band of F color and above, VS clarity and above and Excellent cut, a one carat lab grown diamond ring comes to around a third of the mined price. Mined one carat engagement rings begin from 1,000,000 JPY, while the ANNA DIAMOND one carat solitaire ring on the same quality standard is from 385,000 JPY. The lower price is not a lesser stone. It follows from a different structure, with no mining, with supply that can be planned, and with a short route from the workshop to you. We set out that structure, and how to think about it by budget, in A guide to lab grown diamond prices.
One carat in a single stone and one carat in total are different things
This is where confusion arises most often when looking up the price of one carat. Two pieces can both carry 1ct in the product name, one holding a single stone of one carat, the other gathering small stones to a total of one carat. The prices are far apart.
SINGLE STONE
One carat in a single stone
This is the arrangement with the most presence seen face on.
TOTAL WEIGHT
One carat in total
It carries a lightness that is easy to wear day to day.
Both come to one carat in total weight. Prices include tax and are as of August 2026.
The total weight is the same, and yet the prices differ by around a factor of two. The reason is simple. A larger stone takes longer to grow, and the odds of cutting one out of the rough are lower.
The three things that set the price
Even at the same one carat, prices vary. Three things account for most of that range.
So behind the single phrase one carat costs this much lies quality multiplied by how the stone grew and by how it reached you. Rather than comparing prices alone, it is worth choosing somewhere the reason for the price is visible.
A one carat that is too cheap has a reason
A one carat priced far below the market usually leans toward yellow or brown, or has a shallow cut and a dull return of light, or carries inclusions visible to the naked eye. It weighs one carat without the brilliance a carat leads you to expect.
Checking is not difficult. Are the color, clarity and cut grades stated. Is there a certificate or report from an independent laboratory. Those are the two points to confirm. Which laboratories to trust is covered in our article on certificates as they stand today.
ANNA DIAMOND 4C STANDARDS
COLOR
F and above
D is colorless. Yellow becomes more apparent toward Z
CLARITY
VS and above
The upper six of eleven grades, where inclusions cannot be seen by eye
CUT
Excellent and above
Decided by human skill alone, and not changeable afterward
CERTIFICATE
IGI / 0.5ct and above
The report number lets you trace the record of that stone
The one carat prices at ANNA DIAMOND
Rather than rough figures, here are the prices of the one carat pieces we are selling right now. All include tax and are as of August 2026.
One carat in a single stone from 385,000 JPY, one carat in total from 198,000 JPY. That is the ANNA DIAMOND answer. Every stone is a lab grown diamond of F color and above and VS clarity and above, set into jewelry one piece at a time by craftspeople at our workshop in Kofu, Yamanashi.
Frequently asked questions
How much does a one carat lab grown diamond cost?
At the prices ANNA DIAMOND actually sells at, jewelry with a single one carat stone starts at 385,000 JPY, and jewelry totaling one carat starts at 198,000 JPY, tax included, as of August 2026. Mined diamond engagement rings on the same quality standard usually begin from 1,000,000 JPY, so the level is around a third.
Is one carat too large for everyday wear?
In the round brilliant cut it measures about 6.5mm across. It does carry a clear presence, though depending on the design it settles easily into daily wear. Spreading the light is another way to go, as with a half eternity totaling one carat. If you are unsure, the surest thing is to rest one on your own hand.
Will prices keep falling?
To answer honestly, the market has fallen for several years as growing technology has improved, and that trend may well continue. For that reason we offer these as stones to wear rather than as assets held in the hope of appreciation. The time to buy is not a point in the market but the point at which you want to wear one.
How can I check the quality?
Look for stated color, clarity and cut grades, and for a certificate from an independent laboratory. ANNA DIAMOND provides an IGI certificate with every diamond of 0.5 carats and above.
Can I sell it after buying?
A resale market has not really grown up yet. We offer these as stones to wear and enjoy rather than as something to turn back into money.
After your purchase
ANNA DIAMOND offers returns within seven days, a two year quality guarantee, and free cleaning for life at our own store in Daikanyama. Payment in installments is available with no added fee. Jewelry that is in stock ships within two to five days of your order.
You are welcome to see it in person
The presence of one carat does not come through in a photograph. At the ANNA DIAMOND Gallery in Daikanyama, Tokyo, you can set a single one carat stone and a one carat total side by side on your hand. No appointment is needed.
How prices work, with rough figures by budget, is gathered in A guide to lab grown diamond prices, and the basics of lab grown diamonds in What is a lab grown diamond.
RELATED READING
How to read the 4C of a diamond
Which fields on a certificate to read, and in what order
How to choose a lab grown diamond necklace
How 0.1ct to 1ct reads at the neckline
How to choose an eternity ring
Full against half, and how to settle on size