Skip to content
Diamond Carat Guide: Weight, Size, and Price
Quick Summary: Diamond Carat Guide
A diamond carat guide starts with one fact: carat measures weight, not size. One carat equals 200 milligrams, and a round 1 carat diamond measures about 6.4 to 6.5 mm across. Price, cut, and shape change how big it looks.
- Carat is weight: 1 carat = 200 mg = 100 points.
- A round 0.50 ct stone is about 5 mm, a 1 ct stone about 6.5 mm, a 2 ct stone about 8.1 mm.
- Earring listings show the pair's total weight, so a 2 ct pair is two 1 ct stones.
- Price per carat jumps at "magic sizes" such as 0.50, 0.75, and 1.00 ct.
- Lab-grown diamonds let you size up for less. Pairs start at $342 (as of October 29, 2026).
Last Updated: October 29, 2026
Table of Contents
- What Does Carat Mean in a Diamond?
- How Big Is a 1 Carat Diamond? Carat Size Chart in MM
- Does Carat Weight Equal Size? Why Cut and Shape Matter
- How Much Does a Diamond Cost by Carat Weight?
- What Carat Size Should You Buy?
- Is It Smart to Buy Just Below a Magic Size?
- Frequently Asked Questions
What Does Carat Mean in a Diamond?
Carat is a unit of weight. One metric carat equals 0.2 gram, or 200 milligrams, and it splits into 100 points, so a 0.75 ct stone is a "75 pointer." GIA says carat measures weight, not dimensions, and that cut proportions shape how a stone looks (GIA diamond quality factors).
Do not confuse carat with karat. Karat describes gold purity, such as 10K or 14K. A pair of 1 ct lab diamond stud earrings in 10K white gold uses both words: the diamonds are rated in carats, the metal in karats.
How Big Is a 1 Carat Diamond? Carat Size Chart in MM
A round 1 carat diamond measures about 6.4 to 6.5 mm across the top. A 0.50 ct round is about 5 mm and a 2 ct round is about 8.1 mm. These are typical figures for well-cut rounds. Real stones vary by a few tenths of a millimeter.
Round diamonds drawn to scale, 10 pixels per millimeter. Sizes are typical values, not exact.
| Earring pair (total weight) | Each stone | Approx. diameter | Example, 10K white gold (Oct 29, 2026) |
|---|---|---|---|
| 1 ct | 0.50 ct | 5.0 mm | 1 CT round studs, $342.00 |
| 1.5 ct | 0.75 ct | 5.9 mm | 1.5 CT round studs, $442.50 |
| 2 ct | 1.00 ct | 6.5 mm | 2 CT round studs, $658.50 |
| 3 ct | 1.50 ct | 7.4 mm | 3 CT round studs, $996.00 |
| 4 ct | 2.00 ct | 8.1 mm | 4 CT round studs, $1,288.50 |
Pro Tip: Hold a ruler to your ear in a mirror. Seeing 5 mm next to your lobe tells you more than the number "1 carat" does.
Want to see these sizes on real earrings?
Browse round, pear, oval, emerald, and princess studs from 1 to 4 carats.
Shop Lab-Grown Diamond EarringsDoes Carat Weight Equal Size? Why Cut and Shape Matter
No. Two stones with the same carat weight can look different because shape and depth change the face-up area. GIA ties a diamond's look to cut proportions, not weight alone. A deep stone hides weight in its base. A shallow stone spreads it across the top.
Shape matters most. Elongated shapes such as oval, pear, and emerald cuts often show more surface for the same weight than a round. The same 1 ct pair comes in several shapes on our site: oval at $475.80, pear at $497.25, emerald cut at $486.87, and princess at $453.11, all in 14K yellow gold.
Key Takeaway: Compare millimeters, not just carats. Ask for the diameter, or length and width for fancy shapes, before you buy.
How Much Does a Diamond Cost by Carat Weight?
Price rises with carat, but not in a straight line. Larger stones are rarer, so price per carat climbs. Lab-grown diamonds are real diamonds grown in a laboratory, with essentially the same chemical composition and crystal structure as natural diamonds. The origin is different, and so is the price.
Here is how our round lab-grown stud pairs price per total carat, all 10K white gold, as of October 29, 2026:
| Pair weight | Price | Price per total carat |
|---|---|---|
| 1 ct | $342.00 | $342 |
| 1.5 ct | $442.50 | $295 |
| 2 ct | $658.50 | $329 |
| 3 ct | $996.00 | $332 |
| 4 ct | $1,288.50 | $322 |
Our catalog is not a market-wide price curve. The 1.5 ct pair carries the lowest price per carat here, which shows why checking the actual listing beats assuming bigger always costs more per carat. For loose stones, we currently list a 0.51 ct round lab-grown diamond (D, VS1, IGI certified) at $235 and a 1.02 ct round lab-grown diamond (F, VVS2, IGI certified) at $368. Each shows one unit in stock at the time of writing. See all certified loose diamonds.
What Carat Size Should You Buy?
For everyday studs, most buyers land between 1 and 2 ct total. Choose 1 ct for a quiet daily sparkle, 1.5 to 2 ct for a clear statement, and 3 to 4 ct for a showpiece. For a center stone, 0.50 to 1.00 ct per stone suits most budgets.
Start from how you wear them. If you never take earrings off, size down. If they come out for dinners and weddings, size up. Here are in-stock picks to compare:
- 1 CT round studs in 10K yellow gold, $342.00, for first pairs and daily wear.
- 2 CT round studs in 14K white gold, $744.60, the step up most people notice.
- 4 CT round studs in 14K white gold, $1,402.50, for a statement look.
- Lab diamond basket tennis bracelet in 14K white gold, from $2,055.00, if you want carats on the wrist.
Planning a ring? Use the Build Your Own Engagement Ring page to choose a stone and setting. Many couples pick the shape first and the carat second.
Choosing between two sizes?
Compare pairs side by side and check the listing for weight, metal, and price.
Compare Lab-Grown Diamond StudsIs It Smart to Buy Just Below a Magic Size?
Often, yes. GIA notes that price per carat rises at "magic sizes" such as 0.50, 0.75, and 1.00 ct, and that a stone just over 1.00 ct can sell for about 20 percent more than one just under it. The visual gap between 0.98 and 1.01 ct is negligible.
Ask for stones just below the milestone, such as 0.95 ct instead of 1.00 ct, if face-up size matters more to you than the number on the report. The same idea applies to listings in our certified loose diamonds range. Check cut quality first, since a well-cut 0.95 ct stone can look larger than a poorly cut 1.00 ct.
Watch Out: Earring titles show total pair weight. A "2 CT" listing is two 1 ct stones, not two 2 ct stones. Check this before comparing sizes across stores.
Related Reading
- Diamond Stud Earring Sizes Explained: A Carat-to-Millimeter Chart for Every Budget
- Lab-Grown vs Natural: Diamond Pricing Explained
- What Is a GIA Diamond Certificate? 2026 Guide
- How to Choose the Perfect Engagement Ring: A 2026 Guide
Frequently Asked Questions
How big is a 1 carat diamond in mm?
A well-cut round 1 carat diamond measures about 6.4 to 6.5 mm across. Other shapes measure differently because the weight spreads over a different face-up area.
Is a 2 carat total weight earring pair two 2 carat diamonds?
No. Total weight covers both stones. A 2 ct pair is two stones of about 1 ct each, each near 6.5 mm for a round cut.
Does a bigger carat always cost more per carat?
Usually larger stones cost more per carat because they are rarer, and GIA notes jumps at magic sizes such as 0.50, 0.75, and 1.00 ct. Individual listings vary, so compare the actual price per carat.
What is the difference between carat and karat?
Carat measures a diamond's weight, while karat measures gold purity. A pair of studs in 14K gold with 1 ct total diamond weight uses both.
Are lab-grown diamonds measured in carats the same way?
Yes. Lab-grown diamonds are real diamonds with essentially the same chemical composition and crystal structure as natural diamonds, and they are weighed in carats the same way. The origin is different.
About Databazaar
Databazaar has been selling online since 1999 and has served over 3 million customers. Fine jewelry is a newer line, added in the past year. Prices and stock in this guide are as of October 29, 2026 and can change.
Sources
- GIA, Diamond Quality Factors: https://www.gia.edu/diamond-quality-factor
- JDPN, Round Diamond Size Chart: https://jdpn.nyc/jewelry-industry/jewelers-references/round-diamond-size-chart
- Diamond Screener, Round Diamond Carat Size Chart: https://www.diamondscreener.com/education/round-diamond-carat-size-chart/
- Databazaar product pages and prices, checked October 29, 2026: lab-grown diamond jewelry collection