0.4 Carat Lab-Grown Diamonds
A 0.4 carat diamond is the refined, everyday size: about 4.9 mm across as a round brilliant and 6.3 × 4.3 mm as an oval. Every stone on this page weighs between 0.40 and 0.49 ct, is independently graded by IGI or GIA, and is shown with its live, VAT-inclusive price. Compare shapes below, open any stone to see it true to size on a hand, and set it in a ring with our gemologists when you are ready.
IGI/GIA certified · Inspected in Sweden · Free insured shipping
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How big is a 0.4 carat diamond?
Carat measures weight, not width, so the face-up size of a 0.4 ct diamond depends on its shape and on how deeply it is cut. As a round brilliant it measures about 4.9 mm in diameter. Elongated shapes spread the same weight over a longer outline, which is why a 0.4 ct oval or pear looks noticeably larger from above than a round of the same weight. The table shows the typical face-up measurements of the 0.4 carat stones in our catalogue (median length × width, mm).
| Shape | Typical size of a 0.4 ct stone |
|---|---|
| Round | 4.9 mm |
| Oval | 6.3 × 4.3 mm |
| Pear | 6.8 × 4.3 mm |
| Marquise | 8.0 × 4.0 mm |
| Emerald | 5.3 × 3.6 mm |
| Radiant | 5.5 × 3.8 mm |
| Heart | 5.3 × 4.9 mm |
| Princess | 4.2 mm square |
| Asscher | 4.1 mm square |
On the hand, a 4.9 mm round reads as a neat, precise point of light rather than a statement. It sits low on a slim band, does not catch on clothing, and is the size many people choose for a first engagement ring, a stacking ring, a pendant, or a matched pair of stud earrings, where two 0.4 ct stones give a balanced 0.8 ct total. Open any product and use the "see it true to size" tool to judge it on your own finger.
0.4 carat diamond rings
A 0.4 ct stone suits settings that keep the metal in proportion. A slim solitaire band of around 1.6–2 mm lets the stone lead; a halo of small diamonds around it adds a ring of sparkle and can make the centre read like a stone a size or two larger; a bezel gives a clean, modern outline that is easy to wear every day. Every diamond here is loose and ready to set. Choose "Set this stone in a ring" on the product page or start from the ring configurator, and our gemologists will help you build the setting.
What does a 0.4 carat lab-grown diamond cost?
Prices on this page are live and include VAT, the grading report and insured delivery. Within the 0.40–0.49 ct range, three things move the price: colour, clarity and cut quality. Because a 0.4 ct stone is small, minor inclusions are hard to see without magnification, so an SI1 or VS2 stone is usually clean to the eye, and a G or H colour looks white once it is set. That combination, our Classic tier, is where a 0.4 ct stone gives the most for the money. Diamond prices also rise per carat as weight increases, so a 0.4 ct stone costs well under half of a comparable 1 ct, which is what makes this size a sensible way to buy a higher grade.
Lab-grown pricing puts the whole range within reach: a lab-grown diamond is a real diamond, grown above ground, and typically costs 60–80% less than a mined stone of the same grade. Read how they are grown and graded in our guide to lab-grown diamonds.
Choosing colour, clarity and cut at 0.4 ct
- Cut first. A well-cut stone returns more light and looks larger than a deeper-cut stone of the same weight. Filter for Excellent cut, polish and symmetry.
- Clarity: SI1 to VS2 is enough. At this size inclusions are tiny in absolute terms; pay for VVS only if you want it for its own sake.
- Colour: G–H for value, D–F for an icy look. Small stones show little body colour, so near-colourless grades look white in most settings; colourless D–F stones matter more in platinum or white gold.
- Shape for spread. For the most visible size per carat, look at oval, pear and marquise cuts; for maximum brilliance, round.
Compare nearby sizes
Not sure 0.4 ct is the size? A 0.5 carat diamond is about 0.3 mm wider as a round, and a 0.7 carat diamond is about 5.8 mm. Browse every size, shape and grade together in the diamond search, or see our engagement rings.
0.4 carat diamonds: frequently asked questions
How many mm is a 0.4 carat diamond?
About 4.9 mm in diameter as a round brilliant. Ovals measure roughly 6.3 × 4.3 mm, pears 6.8 × 4.3 mm, emerald cuts 5.3 × 3.6 mm and princess cuts 4.2 mm square. Exact measurements are listed on every certificate and on each product page.
Is a 0.4 carat diamond too small for an engagement ring?
No. It is a deliberately understated choice that suits slim bands, low settings and hands that work. If you want more presence without a heavier stone, a halo setting or an elongated shape such as an oval adds visible size. Use the true-to-size tool on any product to see it on a hand before you decide.
What is 0.4 carat in points and grams?
40 points, or 0.08 g. One carat is divided into 100 points and weighs 0.2 g, so the stones on this page weigh between 40 and 49 points.
Is a lab-grown 0.4 carat diamond a real diamond?
Yes. It has the same crystal structure, hardness and brilliance as a mined diamond; only its origin differs. Every stone here is graded by IGI or GIA and the report states that it is laboratory-grown.
Can I buy two matching 0.4 carat diamonds for earrings?
Yes. Each stone is listed with its exact measurements, colour and clarity, so you can select two that match closely, and our team inspects every stone in Sweden before it ships.
Questions, answered
What 0.4 carat lab-grown diamonds do you offer?
Our 0.4 carat lab-grown diamonds selection features 185 certified lab-grown diamonds in stock right now, each independently graded by IGI or GIA and hand-inspected in Sweden before it ships.
Are lab-grown diamonds real diamonds?
Yes. A lab-grown diamond is a real diamond — chemically, physically and optically identical to a mined one. The only difference is origin: it is grown above ground in a matter of weeks instead of mined over millennia, typically 60–80% less than the mined equivalent.
How are your diamonds certified?
Every stone is independently graded by IGI or GIA and ships with its certificate. You can verify the report number directly on the lab's public website.
Are these diamonds conflict-free?
Yes. Because they are lab-grown, our diamonds are entirely conflict-free and traceable, with a far lower environmental footprint than mined stones.
Can I return a diamond or set it in a ring?
Yes. Every order includes free insured shipping and 30-day returns. Each stone is loose and ready to set — choose "Set this stone in a ring" on any product and our gemologists help you build the setting.
