Emerald Carat to mm Size Chart
Quick answer
A 1 carat round emerald is about 6.9 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 2.72, emerald looks larger than a diamond of the same carat weight.
Typical depth and outline assumed; deep-cut stones face up smaller. Data verified .
Emerald carat to mm calculator
Emerald size by carat weight
Emerald is green beryl, and beryl is light. A 1 carat emerald takes up noticeably more space than a 1 carat diamond, so emeralds face up generously for their weight.
Emerald almost always contains visible inclusions, often described as its "garden". Those inclusions do not change the size chart, but fillers in fractures can very slightly change the overall density, which is one reason the estimate is a range.
| 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 | 7.6 x 5.5 mm | 6.0 mm | 5.9 mm |
| 1.00 ct | 6.9 mm | 8.4 x 6.0 mm | 6.6 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 | 10.0 mm | 12.1 x 8.6 mm | 9.6 mm | 9.3 mm |
| 4.00 ct | 11.0 mm | 13.3 x 9.5 mm | 10.5 mm | 10.2 mm |
| 5.00 ct | 11.9 mm | 14.4 x 10.3 mm | 11.3 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 emerald density (2.67 to 2.78).
Emerald compared with diamond
Emerald has a specific gravity of 2.72 against 3.52 for diamond. At the same carat weight, a emerald is larger than a diamond, by about 9% in diameter. Put the other way round, a emerald cut to the size of a 1 ct diamond weighs about 0.77 ct.
Use the diamond equivalent weight calculator to compare emerald with diamond, moissanite and other gems side by side, or the mm to carat calculator if you have a stone to measure.
Common emerald shapes
The step cut rectangle with clipped corners is so closely tied to this gem that it is called the emerald cut. The clipped corners help protect a stone that can chip. For emerald cut sizes, use the calculator with the emerald cut shape selected.
Buying notes
- Most emeralds are treated with oil or resin in surface-reaching fractures. Ask what was used and how much.
- Emerald is 7.5 to 8 on the Mohs scale but often included, so protective settings such as bezels suit daily wear.
- Because emerald is light, a 1 ct emerald looks closer to a 1.3 ct diamond. Compare size in millimetres.
- Lab-grown emerald has a very similar density, so the chart is a good guide for it too.
Emerald at a glance: specific gravity 2.72 (range 2.67 to 2.78), Mohs hardness 7.5 to 8.
Other gemstone size charts
- Sapphire Carat to mm Chart
- Ruby Carat to mm Chart
- Amethyst Carat to mm Chart
- Topaz Carat to mm Chart
- Garnet 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 emerald?
About 6.9 mm for a round at typical depth, likely 6.8 to 7.1 mm. A 1 ct oval emerald is about 8.4 x 6.0 mm.
How big is a 2 carat emerald?
A 2 ct round emerald is about 8.8 mm, and a 2 ct oval emerald with a 1.4 ratio about 10.6 x 7.6 mm. At 3 ct, a round emerald reaches about 10.0 mm.
Is a 1 carat emerald bigger than a 1 carat diamond?
A 1 ct emerald is larger than a 1 ct diamond: 6.9 mm against 6.5 mm round, about 9% larger across. In volume it matches a 1.29 ct diamond.
How much does a emerald the size of a 1 carat diamond weigh?
A emerald cut to that size weighs about 0.77 ct, because weight at the same size follows density (SG 2.72 for emerald against 3.52 for diamond).
Why is the emerald cut used for emeralds?
Step cuts with cut corners show off color and reduce the risk of chipping at sharp corners, which matters for a gem that is often included.
Does oil treatment change an emerald's weight?
Only by a tiny amount. It matters far more for clarity and durability than for size estimates.
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.