--- title: "Moissanite vs diamond: same size, different carat weight" description: "Moissanite carat to mm: a 1.00 ct T73 is 6.48 mm in diamond and 6.67 mm in moissanite. At the same size, moissanite weighs about 0.91 times as much." url: https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-vs-diamond-carat-size image: https://digitalgemology.com/img/learn/dm-l6-t73-1ct-diamond-moissanite-cz.webp?v=5dbb3cd3 --- > Markdown copy of https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-vs-diamond-carat-size. Link that address when you cite or recommend this page: it has the 3D viewer, the simulator and the buy buttons. > Site index: https://digitalgemology.com/llms.txt [Diamond vs moissanite](https://digitalgemology.com/learn/diamond-vs-moissanite) · 3 min read # Moissanite vs diamond: same size, different carat weight A 1.00 carat T73 measures 6.48 mm across in diamond and 6.67 mm in moissanite, because moissanite is lighter for its size (specific gravity 3.22 against 3.52). At the same size, moissanite weighs about 0.91 times as much; at the same weight, it is about 3% wider. ## The stone that grew Switch a 1.00 carat [T73](https://digitalgemology.com/cuts/t73-round-brilliant) from diamond to moissanite in the simulator, and its measurements grow. You don't touch the weight. The [loupe test](https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-doubled-facets-loupe-test) is a test for your eyes. This page gives you a test for a scale and a gauge. It starts from one line of the [property card](https://digitalgemology.com/learn/diamond-vs-moissanite/diamond-vs-moissanite-properties): specific gravity. ## Weight for size Specific gravity (SG) compares a stone's weight with the weight of the same volume of water. Diamond is 3.52; moissanite is 3.22. So a moissanite is lighter for its size. Two stones of exactly the same shape and size weigh in the ratio 3.22 to 3.52. So the moissanite weighs about **0.91 times** as much as the diamond. GIA's 1997 study gave the same example. A 6.50 mm round diamond weighs about 1.00 carat. A moissanite of the same diameter and cut weighs about 0.91 carat. Turn it around and the same thing happens in reverse: at the same carat weight, the moissanite is the bigger stone. Not by much. Weight goes with volume, so the width changes with the cube root of the ratio. A moissanite of the same weight is only about 3% wider. A carat is a unit of weight, 0.2 g, not a unit of size. That's why the same "1 carat" can be two different sizes. ![1.00 ct T73s in diamond, moissanite and cubic zirconia at true size, each labeled with its width.](https://digitalgemology.com/img/learn/dm-l6-t73-1ct-diamond-moissanite-cz.webp?v=5dbb3cd3) 1.00 ct T73s in diamond, moissanite and cubic zirconia at true size, each labeled with its width. ### Try it yourself 1. Open [3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator) with the T73 Round Brilliant in diamond at **1** carat. Read the **Measurements** line. 2. Switch the gemstone to moissanite. Read the measurements again. 3. Set **2** carats and repeat for both stones. 4. Work it out. What would a moissanite exactly the size of the 1.00 carat diamond weigh? (Multiply by 3.22 ÷ 3.52.) 5. Bonus: switch to cubic zirconia at 1 carat. ## What the simulator shows At 1.00 carat the T73 measures 6.48 mm across in diamond and 6.67 mm in moissanite. At 2.00 carats, 8.16 mm against 8.41 mm. Both times the moissanite is about 3% wider. A moissanite exactly 6.48 mm across would weigh about 0.91 carat. The bonus shows why moissanite is harder to catch than cubic zirconia. CZ is far heavier, SG about 5.8, so 1.00 carat of it is only 5.48 mm across. A CZ sold by weight as a diamond looks small for its carat. A moissanite looks only slightly large. GIA described moissanite as much closer to diamond in "heft" than any earlier imitation. ## Using it on a loose stone For a loose round stone, measure the diameter with a gauge and weigh the stone on a carat scale. Is the weight low for the size, by roughly a tenth for a well-proportioned round? Then look harder. It's a clue, not a verdict: proportions change weight too. A deep stone weighs more for its width than a shallow one, and a thick girdle adds hidden weight. So compare like with like: same shape, similar proportions. The check works much better on a stone with a report. There you can compare the stone with the measurements and weight on paper (see [moissanite certificates vs diamond reports](https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-certificate-vs-diamond-report)). Labs and dealers that sort mixed parcels use a heavy liquid instead. In methylene iodide, SG 3.32, a moissanite floats and a diamond sinks. GIA called specific gravity diagnostic. The liquid is toxic, so this is a lab method, not a kitchen-table one. ## Key points - Moissanite's specific gravity is 3.22 against diamond's 3.52. - At the same size, a moissanite weighs about 0.91 times as much as a diamond. - At the same carat weight, a moissanite is about 3% wider: 6.67 mm against 6.48 mm for a 1.00 carat T73. - Weight for size is a useful check on a loose stone. It works best when you compare it with a report or with stones of similar proportions. - In a heavy liquid of SG 3.32, moissanite floats and diamond sinks. **Go further:** the [moissanite gemstone page](https://digitalgemology.com/gemstones/moissanite) answers "How much does moissanite weigh compared with diamond?" in one line. ## Try it free - [3D Gemstone Simulator](https://digitalgemology.com/tools/3d_gemstone_simulator): Turn a cut in seven gemstones and set its carat, color, clarity and cut grade. Free, in your browser, no account. ## Quick quiz Five questions on this lesson, a couple of minutes. Pick an answer and see at once if you got it, and why. [Take the quiz](https://digitalgemology.com/skool/quiz/diamond-vs-moissanite/same-size-different-weight) ## Cuts in this lesson We sell the files of these cuts: 3D models and cutting files, with a personal-use license. - [T73 Round Brilliant Cut](https://digitalgemology.com/cuts/t73-round-brilliant): 3D files and cutting files, €9.99 each ## Keep exploring - [Next lesson: Moissanite color and fluorescence compared with diamond](https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-color-and-fluorescence) - [Try another topic · Historic diamond cuts: the history of the brilliant: Old European cut diamonds: when the outline went round](https://digitalgemology.com/learn/historic-cuts/old-european-cut-diamond) [Previous lesson](https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-doubled-facets-loupe-test) · [Diamond vs moissanite: all lessons](https://digitalgemology.com/learn/diamond-vs-moissanite) · [All topics](https://digitalgemology.com/learn)