Garnet Carat to mm Size Chart
Quick answer
A 1 carat round garnet is about 6.1 mm across and a 2 carat about 7.7 mm. A 1 ct oval is about 7.4 x 5.3 mm. With a specific gravity of 4.05, garnet looks smaller than a diamond of the same carat weight.
Typical depth and outline assumed; deep-cut stones face up smaller. Data verified .
Garnet carat to mm calculator
Garnet size by carat weight
Garnet is not one material but a family. Almandine, the deep red garnet most people picture, is used for the chart below. Other garnets vary in density, so their sizes shift a little, and the calculator lets you choose each one.
Almandine is dense, close to ruby and sapphire, so it faces up smaller than a diamond of the same weight. Rhodolite, pyrope and tsavorite are lighter than almandine. Spessartine is a little denser.
| Carats | Round | Oval (1.4 ratio) | Cushion | Diamond round, same weight |
|---|---|---|---|---|
| 0.25 ct | 3.8 mm | 4.6 x 3.3 mm | 3.7 mm | 4.1 mm |
| 0.50 ct | 4.8 mm | 5.8 x 4.2 mm | 4.6 mm | 5.1 mm |
| 0.75 ct | 5.5 mm | 6.7 x 4.8 mm | 5.3 mm | 5.9 mm |
| 1.00 ct | 6.1 mm | 7.4 x 5.3 mm | 5.8 mm | 6.5 mm |
| 1.50 ct | 7.0 mm | 8.4 x 6.0 mm | 6.7 mm | 7.4 mm |
| 2.00 ct | 7.7 mm | 9.3 x 6.6 mm | 7.3 mm | 8.1 mm |
| 3.00 ct | 8.8 mm | 10.6 x 7.6 mm | 8.4 mm | 9.3 mm |
| 4.00 ct | 9.7 mm | 11.7 x 8.3 mm | 9.2 mm | 10.2 mm |
| 5.00 ct | 10.4 mm | 12.6 x 9.0 mm | 9.9 mm | 11.0 mm |
Generated by our formula engine at typical depth: 61% of width for rounds and ovals, 70% for cushions. Round sizes carry a range of about plus or minus 3% that comes from the spread in published factors and in garnet density (3.93 to 4.30).
Garnet compared with diamond
Garnet has a specific gravity of 4.05 against 3.52 for diamond. At the same carat weight, a garnet is smaller than a diamond, by about 5% in diameter. Put the other way round, a garnet cut to the size of a 1 ct diamond weighs about 1.15 ct.
Use the diamond equivalent weight calculator to compare garnet with diamond, moissanite and other gems side by side, or the mm to carat calculator if you have a stone to measure.
Common garnet shapes
Rounds, ovals, cushions and pears are common. Garnet is also popular in small calibrated sizes for vintage-style clusters and in cabochon form.
Buying notes
- Ask which garnet you are buying. The name changes the density, the size estimate and usually the price.
- Garnets are generally sold without treatment, which makes them a straightforward buy.
- At 7 to 7.5 on the Mohs scale, garnet is fine for most jewelry but can show wear on facet edges in rings worn every day.
- Dark almandine can look almost black in small sizes. Size up or choose a lighter garnet for brightness.
Garnet at a glance: specific gravity 4.05 (range 3.93 to 4.30), Mohs hardness 7 to 7.5. Garnet is a family. Density varies with chemistry.
Other gemstone size charts
- Sapphire Carat to mm Chart
- Ruby Carat to mm Chart
- Emerald Carat to mm Chart
- Amethyst Carat to mm Chart
- Topaz Carat to mm Chart
- Aquamarine Carat to mm Chart
- Spinel Carat to mm Chart
- Cubic Zirconia Carat to mm Chart
- Diamond size chart in mm
- Gemstone specific gravity chart
Related questions
How many mm is a 1 carat garnet?
About 6.1 mm for a round at typical depth, likely 5.9 to 6.3 mm. A 1 ct oval garnet is about 7.3 x 5.2 mm.
How big is a 2 carat garnet?
A 2 ct round garnet is about 7.7 mm, and a 2 ct oval garnet with a 1.4 ratio about 9.3 x 6.6 mm. At 3 ct, a round garnet reaches about 8.8 mm.
Is a 1 carat garnet bigger than a 1 carat diamond?
A 1 ct garnet is smaller than a 1 ct diamond: 6.1 mm against 6.5 mm round, about 5% smaller across. In volume it matches a 0.87 ct diamond.
How much does a garnet the size of a 1 carat diamond weigh?
A garnet cut to that size weighs about 1.15 ct, because weight at the same size follows density (SG 4.05 for garnet against 3.52 for diamond).
Which garnet is the chart for?
Almandine. For rhodolite, pyrope, spessartine or tsavorite, choose them in the calculator. Their densities are marked approximate because published values vary.
Is garnet heavier than diamond?
Almandine and spessartine are. Pyrope, rhodolite and tsavorite are a little denser than diamond too, but closer to it.
Sources and method
Weight estimates use the colored-stone shape factors published by the International Gem Society and the Dendritics standard formula, and the diamond trade constants and length to width ratio tables published in jewelry trade references (Esslinger, Omni, Octonus). Specific gravity values are cross-checked against the International Gem Society density tables, the USGS Natural Gemstones report and GemSelect.
Every number on this page is generated by the same formula engine as the calculators. Read the full method, constants and limits and the editorial policy. Data last verified 2026-11-04.
Estimates only. This is not an appraisal, grading report or valuation. A calibrated scale or a lab report is the only real weight.