Diamond Cut Score (Length to Width Ratio) Calculator
This calculator helps determine the length-to-width ratio of a diamond, a key factor in assessing its shape appeal, especially for non-round cuts, but also relevant for round cuts to check for symmetry deviations.
Enter the diamond's **Length** and **Width** (typically in millimeters) to calculate the ratio and get an interpretation based on common standards for round diamonds.
Enter Diamond Dimensions
Understanding Length to Width Ratio
What is the Length to Width Ratio?
The length-to-width ratio of a diamond is calculated by dividing its length (longest dimension) by its width (widest dimension perpendicular to the length). This ratio is a key factor in determining the face-up shape of a diamond.
Why is it Important?
For **fancy shapes** (non-round diamonds like oval, pear, marquise, emerald, etc.), the ratio dictates how elongated or wide the diamond appears. Personal preference plays a significant role here, as some people prefer a more elongated shape while others prefer a wider one.
For **round brilliant** diamonds, the ideal length-to-width ratio is as close to **1.00** as possible. A ratio significantly deviating from 1.00 in a round diamond often indicates poor symmetry or an unintended shape, which can negatively impact its appearance and value.
Formula
Length to Width Ratio = Length / Width
Typical Ratio Ranges (for Round Diamonds)
While personal preference varies for fancy shapes, common interpretations for **Round Brilliant** diamonds based on ratio include:
- Excellent/Ideal: 1.00 - 1.02
- Very Good: 1.03 - 1.05
- Good: 1.06 - 1.10
- Fair: 1.11 - 1.15
- Poor: > 1.15 or < 1.00
This calculator provides an interpretation based on these common ranges for round diamonds.
Length to Width Ratio Examples
See how different dimensions affect the ratio:
Example 1: Perfectly Round Diamond
Input: Length = 5.0 mm, Width = 5.0 mm
Calculation: Ratio = 5.0 / 5.0 = 1.00
Result: Ratio = 1.00, Interpretation = Excellent/Ideal for Round
Conclusion: A perfectly balanced round diamond.
Example 2: Slightly Off-Round Diamond
Input: Length = 5.1 mm, Width = 5.0 mm
Calculation: Ratio = 5.1 / 5.0 = 1.02
Result: Ratio = 1.02, Interpretation = Excellent/Ideal for Round
Conclusion: Still within the ideal range for a round diamond.
Example 3: Minor Symmetry Issue in Round
Scenario: A round diamond measures slightly longer than wide.
Input: Length = 5.3 mm, Width = 5.0 mm
Calculation: Ratio = 5.3 / 5.0 = 1.06
Result: Ratio = 1.06, Interpretation = Good for Round
Conclusion: This might be noticeable as slightly off-round to a discerning eye.
Example 4: Oval Cut Diamond (Typical)
Scenario: A common ratio for an oval cut diamond.
Input: Length = 8.0 mm, Width = 5.3 mm
Calculation: Ratio = 8.0 / 5.3 ≈ 1.51
Result: Ratio ≈ 1.51, Interpretation = N/A (Ratio for fancy shape)
Conclusion: A typical, pleasing ratio for an oval diamond.
Example 5: Elongated Pear Cut Diamond
Scenario: A pear shape with a more elongated look.
Input: Length = 9.0 mm, Width = 5.0 mm
Calculation: Ratio = 9.0 / 5.0 = 1.80
Result: Ratio = 1.80, Interpretation = N/A (Ratio for fancy shape)
Conclusion: This pear would appear quite long and slender.
Example 6: Wider Cushion Cut Diamond
Scenario: A cushion cut with a squarer, less elongated profile.
Input: Length = 6.5 mm, Width = 6.0 mm
Calculation: Ratio = 6.5 / 6.0 ≈ 1.08
Result: Ratio ≈ 1.08, Interpretation = N/A (Ratio for fancy shape)
Conclusion: This cushion is close to square, having a low length-to-width ratio.
Example 7: Marquise Cut Diamond
Scenario: A typical length-to-width ratio for a marquise.
Input: Length = 10.0 mm, Width = 5.0 mm
Calculation: Ratio = 10.0 / 5.0 = 2.00
Result: Ratio = 2.00, Interpretation = N/A (Ratio for fancy shape)
Conclusion: Marquise cuts often have ratios around 2.00 or higher.
Example 8: Radiant Cut Diamond
Scenario: An elongated radiant cut.
Input: Length = 7.5 mm, Width = 5.0 mm
Calculation: Ratio = 7.5 / 5.0 = 1.50
Result: Ratio = 1.50, Interpretation = N/A (Ratio for fancy shape)
Conclusion: A common ratio for an elongated radiant cut.
Example 9: Round Diamond (Very Poor Symmetry)
Scenario: A round diamond with significant asymmetry.
Input: Length = 5.5 mm, Width = 5.0 mm
Calculation: Ratio = 5.5 / 5.0 = 1.10
Result: Ratio = 1.10, Interpretation = Good for Round
Conclusion: While mathematically 'Good', a ratio this high might indicate visible distortion in a 'round' diamond.
Example 10: Round Diamond (Extreme Poor Symmetry)
Scenario: A round diamond that is clearly not round.
Input: Length = 6.0 mm, Width = 5.0 mm
Calculation: Ratio = 6.0 / 5.0 = 1.20
Result: Ratio = 1.20, Interpretation = Poor for Round (Too Elongated)
Conclusion: A ratio this high means the diamond is far from round and would likely be classified differently or have a significant symmetry defect.
Frequently Asked Questions about Diamond Length to Width Ratio
1. What is the length to width ratio?
It's a measure of how elongated or wide a diamond appears, calculated by dividing the longest dimension (length) by the widest dimension perpendicular to the length (width).
2. Why is this ratio important for diamonds?
For fancy shapes (non-round), it determines the aesthetic outline (e.g., how slender or wide an oval looks), based purely on personal preference. For round diamonds, it's a critical indicator of symmetry – a ratio close to 1.00 is ideal.
3. What is an ideal length to width ratio for a round diamond?
An ideal ratio for a round brilliant diamond is 1.00, meaning its length and width are equal. Ratios between 1.00 and 1.02 are generally considered excellent or ideal.
4. What do the interpretation labels (Excellent, Good, Poor) mean?
These labels are based on common industry standards specifically for **round brilliant** diamonds to indicate how close the ratio is to the ideal 1.00. For fancy shapes, these labels don't apply; the 'ideal' ratio is subjective.
5. Does the ratio affect a diamond's sparkle (brilliance/fire)?
The length-to-width ratio primarily affects the diamond's shape outline. While extreme deviations in a round stone might be caused by cut issues that also affect sparkle, the ratio itself is a measure of shape, not light performance (which is more related to depth, table, facet angles, polish, and symmetry).
6. How is the length and width of a diamond measured?
These dimensions are measured using precise tools by gemologists or appraisers. They are typically provided on a diamond's grading report (like GIA or AGS).
7. Can I use this calculator for fancy shapes?
Yes, absolutely! You can calculate the ratio for any diamond shape using its length and width. The interpretation provided by the tool is based on round diamond standards, so for fancy shapes, just look at the calculated ratio and compare it to typical ranges for that specific fancy shape or your personal preference.
8. What are typical length to width ratios for popular fancy shapes?
Typical ranges (highly subjective) are: Oval (1.35-1.55), Pear (1.50-1.75), Marquise (1.85-2.10), Emerald (1.30-1.60), Radiant (1.00-1.05 for square, 1.20-1.50+ for rectangular), Princess (1.00-1.05 for square, 1.05+ for rectangular), Cushion (1.00-1.05 for square, 1.10-1.20 for rectangular).
9. What if the width is greater than the length?
In fancy shapes, the 'length' is defined as the longest dimension. In a round diamond, if the measured 'width' is greater than the measured 'length', the calculated ratio will be less than 1.00. For a round diamond, a ratio below 1.00 also indicates asymmetry or poor shape and falls into the 'Poor' interpretation category.
10. Can a high length-to-width ratio in a round diamond affect setting?
Yes, a round diamond with a noticeable deviation from 1.00 might look slightly distorted and could potentially require a custom setting to appear truly round or to fit securely, although minor deviations are usually fine in standard settings.
