Aquamarine Carat to mm Size Chart
Quick answer
A 1 carat round aquamarine is about 7.0 mm across and a 2 carat about 8.8 mm. A 1 ct oval is about 8.4 x 6.0 mm. With a specific gravity of 2.69, aquamarine looks larger than a diamond of the same carat weight.
Typical depth and outline assumed; deep-cut stones face up smaller. Data verified .
Aquamarine carat to mm calculator
Aquamarine size by carat weight
Aquamarine is blue to blue-green beryl, a sister of emerald. It is light, so aquamarine gives one of the largest looks per carat among popular gems.
Unlike emerald, aquamarine is often clean, so it is commonly cut in larger sizes, where its light density makes a big difference to face-up size.
| Carats | Round | Oval (1.4 ratio) | Cushion | Diamond round, same weight |
|---|---|---|---|---|
| 0.25 ct | 4.4 mm | 5.3 x 3.8 mm | 4.2 mm | 4.1 mm |
| 0.50 ct | 5.5 mm | 6.7 x 4.8 mm | 5.3 mm | 5.1 mm |
| 0.75 ct | 6.3 mm | 7.7 x 5.5 mm | 6.1 mm | 5.9 mm |
| 1.00 ct | 7.0 mm | 8.4 x 6.0 mm | 6.7 mm | 6.5 mm |
| 1.50 ct | 8.0 mm | 9.6 x 6.9 mm | 7.6 mm | 7.4 mm |
| 2.00 ct | 8.8 mm | 10.6 x 7.6 mm | 8.4 mm | 8.1 mm |
| 3.00 ct | 10.1 mm | 12.2 x 8.7 mm | 9.6 mm | 9.3 mm |
| 4.00 ct | 11.1 mm | 13.4 x 9.6 mm | 10.6 mm | 10.2 mm |
| 5.00 ct | 11.9 mm | 14.4 x 10.3 mm | 11.4 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 aquamarine density (2.66 to 2.74).
Aquamarine compared with diamond
Aquamarine has a specific gravity of 2.69 against 3.52 for diamond. At the same carat weight, a aquamarine is larger than a diamond, by about 9% in diameter. Put the other way round, a aquamarine cut to the size of a 1 ct diamond weighs about 0.76 ct.
Use the diamond equivalent weight calculator to compare aquamarine with diamond, moissanite and other gems side by side, or the mm to carat calculator if you have a stone to measure.
Common aquamarine shapes
Emerald cuts, ovals and cushions are the classic aquamarine shapes. Long step cuts show off its pale color well, and large stones of several carats are common in pendants and cocktail rings.
Buying notes
- Most aquamarine is heated to remove green tones and produce a purer blue. Ask for disclosure.
- Pale stones look paler in small sizes. Size matters more for color with aquamarine than with darker gems.
- At 7.5 to 8 on the Mohs scale it is durable for most jewelry.
- Because it is light, check that a setting made for a diamond of the same carat weight is not too small.
Aquamarine at a glance: specific gravity 2.69 (range 2.66 to 2.74), Mohs hardness 7.5 to 8. Sources cluster at 2.67 to 2.71.
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
- Garnet 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 aquamarine?
About 7.0 mm for a round at typical depth, likely 6.8 to 7.1 mm. A 1 ct oval aquamarine is about 8.4 x 6.0 mm.
How big is a 2 carat aquamarine?
A 2 ct round aquamarine is about 8.8 mm, and a 2 ct oval aquamarine with a 1.4 ratio about 10.6 x 7.6 mm. At 3 ct, a round aquamarine reaches about 10.1 mm.
Is a 1 carat aquamarine bigger than a 1 carat diamond?
A 1 ct aquamarine is larger than a 1 ct diamond: 7.0 mm against 6.5 mm round, about 9% larger across. In volume it matches a 1.31 ct diamond.
How much does a aquamarine the size of a 1 carat diamond weigh?
A aquamarine cut to that size weighs about 0.76 ct, because weight at the same size follows density (SG 2.69 for aquamarine against 3.52 for diamond).
Is aquamarine the same size per carat as emerald?
Very close. Both are beryl and their densities overlap, so their sizes per carat are almost the same.
How big is a 5 carat aquamarine?
Large. The chart below gives round, oval and cushion sizes for 5 ct, generated from aquamarine density.
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.