Diamond Length-to-Width Ratio Calculator
Understanding the Diamond Ratio: Why It Matters
When shopping for a diamond, the 4 Cs (Cut, Color, Clarity, and Carat) are essential, but for fancy-shaped diamonds, the Length-to-Width (L/W) Ratio is equally important. This mathematical ratio determines the overall silhouette and visual balance of the stone, indicating whether a diamond appears "fat," "skinny," or "perfectly proportioned."
What is the Diamond Ratio?
The diamond ratio is calculated by dividing the length of the diamond by its width. For example, if an oval diamond has a length of 9.0mm and a width of 6.0mm, its ratio is 1.50 (9.0 / 6.0 = 1.50).
Example Calculation:
- Length: 7.50 mm
- Width: 5.00 mm
- Formula: 7.50 รท 5.00 = 1.50
- Result: 1.50 L/W Ratio
Ideal Ratios for Different Diamond Shapes
Every diamond shape has an "ideal" ratio range that is traditionally preferred by gemologists and collectors for maximum aesthetic appeal. Use the table below to compare your results:
| Diamond Shape | Ideal Ratio Range |
|---|---|
| Round Brilliant | 1.00 – 1.01 (Perfectly Circular) |
| Princess Cut | 1.00 – 1.04 (Square) |
| Oval | 1.30 – 1.50 |
| Emerald Cut | 1.30 – 1.50 |
| Pear Shape | 1.45 – 1.75 |
| Marquise | 1.85 – 2.10 |
| Radiant (Square) | 1.00 – 1.05 |
| Radiant (Rectangular) | 1.20 – 1.50 |
| Cushion (Square) | 1.00 – 1.05 |
How the Ratio Affects Your Diamond
The ratio affects more than just the look; it affects how the stone wears on the finger:
- High Ratios: Diamonds with higher ratios (like 1.70+ for Marquise or Pear) create an elongating effect on the finger, making it look slimmer.
- Low Ratios: Lower ratios provide a more substantial, wider look. A lower ratio in an Oval can make it look like a "Movall" (Marquise-Oval hybrid).
- Symmetry: While personal preference varies, ratios outside the "ideal" range may impact the light performance and create "bow-tie" effects in Ovals and Pears.
Frequently Asked Questions
Does the ratio affect the price?
Not directly, but "perfect" ratios are in higher demand. A stone with a classic 1.50 ratio for an Oval may command a slightly higher premium than one that is overly wide or overly narrow, as it is easier to sell.
Is a 1.0 ratio always best?
Only for shapes intended to be square or round. For fancy shapes like Emeralds or Ovals, a 1.0 ratio would result in a square or round look, losing the characteristic elegance of the elongated cut.
How do I find the dimensions?
You can find the precise length and width measurements on the diamond's grading report (such as GIA, IGI, or AGS) under the "Measurements" section. They are typically listed as Length x Width x Depth.