Diamond Table Percentage Calculator – Understand Table, Depth, Crown And Pavilion
This Diamond Table Percentage Calculator helps you turn simple millimeter measurements into clear proportion numbers. By entering your table size, minimum and maximum girdle diameter, total depth and optionally crown height and pavilion depth, you can compute table %, depth %, crown % and pavilion %. The tool then compares those values to typical proportion bands for the selected shape and summarizes how well your diamond fits within them.
Instead of guessing whether a table is too large or a depth is too deep, you can see the exact percentages and how they compare with shape-specific guidelines. The calculator also provides a simple proportion grade such as Excellent, Very Good, Good, Fair or Poor based on how many of your values fall inside ideal or acceptable ranges.
Key Formulas Used In This Diamond Proportion Calculator
All of the calculations revolve around the average girdle diameter. Many diamonds are slightly out-of-round, so grading systems use the average of minimum and maximum diameters as the reference.
Once AverageDiameter is known, each vertical measurement is converted into a percentage of that diameter.
Diamond table percentage formula
TableSize is the width of the flat top facet measured in millimeters. A higher table percentage means a relatively large table compared to the spread of the diamond.
Diamond depth percentage formula
TotalDepth is the full height of the diamond from table to culet. A deeper diamond has a higher depth percentage, while a shallow diamond has a lower depth percentage. Both extremes can affect light performance.
Crown and pavilion percentage formulas
Pavilion% = (PavilionDepth ÷ AverageDiameter) × 100
CrownHeight measures how high the crown rises above the girdle, and PavilionDepth measures how far the pavilion extends below it. These percentages help describe how the upper and lower halves of the diamond are proportioned around the girdle.
Shape-Based Ideal Ranges For Table And Depth
Different shapes aim for different proportion ranges. A round brilliant with a mid-50s table percentage can be desirable, while some princess and radiant cuts can have higher table percentages and still be considered attractive. The calculator includes suggested bands for several popular shapes.
- Round brilliant: often modeled with table percentages in the mid-50% range and depth percentages around the low 60% range.
- Oval, cushion and pear: allow somewhat wider table and depth bands due to stretched shapes and style variation.
- Princess, emerald and radiant: can support higher table percentages and slightly deeper depths without looking overly deep.
- Marquise and asscher: use elongated or step-cut profiles, so acceptable proportions can vary more by design.
The calculator stores an ideal band and a broader acceptable band for table and depth percentages for each shape. It then checks whether your table and depth fall inside those bands and uses that information when assigning a proportion grade.
How The Calculator Grades Overall Proportions
The proportion grade is produced in two steps. First, each available metric (table %, depth %, crown % and pavilion %) is classified relative to ideal and acceptable ranges.
Score = 2 if value is inside the ideal band
Score = 1 if value is inside the acceptable band
Score = 0 if value falls outside both bands
Metrics that you do not enter, such as crown or pavilion when left blank, are ignored. The calculator sums the scores and divides by the maximum possible score for the metrics that were actually used to obtain an average score between 0 and 1.
This AverageScore is then mapped to an overall grade.
Very Good: 0.70 ≤ AverageScore < 0.85
Good: 0.50 ≤ AverageScore < 0.70
Fair: 0.30 ≤ AverageScore < 0.50
Poor: AverageScore < 0.30
The result is a simple verbal summary that reflects how consistently your measurements fall within the suggested ranges for the chosen shape.
Why Table And Depth Percentages Are So Important
While many advanced cut grading systems use angles, symmetry and light performance data, table and depth percentages remain core descriptors of a diamond’s shape. They help answer questions such as whether a stone has been cut too shallow to maximize spread or too deep, potentially trapping light inside.
- A table percentage that is too high can make the diamond look flat, with less fire from the crown facets.
- A table percentage that is too low can make the crown appear too steep and reduce brightness.
- A depth percentage that is too low may lead to light leakage through the pavilion, reducing sparkle.
- A depth percentage that is too high can concentrate weight in the pavilion and make the stone face up smaller.
By pairing table % and depth % with crown % and pavilion %, the calculator provides a fuller picture of how material is distributed relative to the diamond’s footprint.
Using The Calculator With Measurements From A Grading Report
If you have a grading report that already lists table and depth percentages, you can still use the calculator to check consistency. One approach is to reverse-engineer the implied measurements.
- Take the average diameter and multiply by the table percentage to approximate table size.
- Take the average diameter and multiply by the depth percentage to approximate total depth.
- Enter those values together with your measured diameters to see whether the calculated percentages match the report within rounding.
This process can give you confidence that the reported numbers and your measurements align, or highlight when something may have been rounded or approximated differently.
How To Use The Diamond Table Percentage Calculator Step-By-Step
- Select the diamond shape that most closely matches your stone, such as round, oval, princess or emerald.
- Measure or read the table size in millimeters and enter it into the table size field.
- Enter the minimum and maximum girdle diameters; if the stone is very round, they may be nearly identical.
- Enter the total depth from table to culet. If you have crown height and pavilion depth, enter them as well for more detail.
- Optionally, add carat weight for your own reference; the calculator uses it only for context in the interpretation.
- Click the calculation button to see table %, depth %, crown % and pavilion % expressed relative to the average diameter.
- Review the ideal and acceptable ranges shown for your selected shape and read the proportion grade summary.
Limitations And Best Practices
This calculator focuses on geometry, not light performance. Real cut grading also looks at angles, symmetry, polish and advanced optical measurements. Use the tool as an educational guide rather than a substitute for laboratory cut grades.
- Ensure measurements are taken carefully, ideally with calibrated tools.
- Remember that different labs and brands may use slightly different proportion targets.
- Use the proportion grade to compare stones or understand a report, not as the only decision factor.
Diamond Proportion FAQs
Frequently Asked Questions About Diamond Table And Depth Percentages
Clarify how table %, depth %, crown % and pavilion % interact when judging diamond proportions and how to use this calculator alongside professional grading reports.
Not always. Some modern cuts and fancy shapes intentionally use higher table percentages for stylistic reasons. The key is whether the table percent sits in a sensible range for that shape and whether it works together with depth, crown and pavilion to support light performance. The calculator therefore interprets table % relative to the chosen shape instead of using a single universal target.
You can still use the calculator with just table size, diameters and total depth. In that case, only table % and depth % are used for the proportion grade, and crown and pavilion are shown as not available. This still provides useful insight into how your diamond compares with common table and depth bands.
No. Percentages depend only on distances relative to the average diameter, so the formulas remain the same for any carat weight. However, larger stones often reveal proportion issues more visibly, so carat weight is still an important context for interpreting the numbers and deciding how strict you want to be about proportion ranges.
Yes. Proportion formulas and percentage ranges apply to both natural and laboratory-grown diamonds. The origin of the diamond affects how it was formed, not how its physical dimensions are measured or interpreted in terms of table and depth percentages.
Measurements to the nearest 0.01 mm are ideal, but even values rounded to 0.02–0.05 mm can provide a useful picture, especially when they come from a grading report. Small rounding differences may change the percentages slightly but rarely enough to move a stone from an excellent band to a poor band in this simplified model.