Calculate a diamond’s length-to-width ratio from length and width, or find the missing length, width, or ratio in inches, feet, cm, or meters.
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Diamond Length-to-Width Ratio (L/W) Formula
The diamond length-to-width ratio compares the longest dimension of the diamond to its width. The calculator can solve for the ratio, the length, or the width when you enter any two positive values.
LWR = L / W
L = LWR * W
W = L / LWR
- LWR = length-to-width ratio
- L = diamond length, measured along the longest dimension
- W = diamond width, measured across the shorter dimension
If you enter length and width, the calculator divides length by width to find the L/W ratio. If you enter width and the ratio, it multiplies them to find length. If you enter length and the ratio, it divides length by the ratio to find width.
The calculator converts length and width to inches internally before doing the calculation. This allows you to use different supported units, such as inches, feet, centimeters, and meters. The final missing length or width is then converted back to the unit selected for that field.
Typical Diamond Length-to-Width Ratio Ranges by Shape
These ranges are common visual preferences, not strict grading rules. The best ratio depends on the diamond shape and the look you want.
| Diamond shape | Common L/W ratio range | General appearance |
|---|---|---|
| Round | 1.00 | Circular |
| Princess or square cushion | 1.00 to 1.05 | Square to very slightly rectangular |
| Oval | 1.30 to 1.50 | Balanced elongated oval |
| Emerald | 1.30 to 1.50 | Classic rectangle |
| Radiant | 1.00 to 1.45 | Square through elongated rectangle |
| Pear | 1.45 to 1.75 | Teardrop shape with moderate length |
| Marquise | 1.75 to 2.25 | Long, narrow outline |
Supported Unit Conversions
| Unit | Conversion to inches |
|---|---|
| Inches | 1 in = 1 in |
| Feet | 1 ft = 12 in |
| Centimeters | 1 cm = 0.393701 in |
| Meters | 1 m = 39.3701 in |
Example Problems
Example 1: Calculate the L/W ratio
A diamond has a length of 1.02 cm and a width of 0.68 cm.
LWR = 1.02 / 0.68 = 1.50
The diamond has a length-to-width ratio of 1.50.
Example 2: Calculate the missing width
A diamond has a length of 1.05 cm and a target L/W ratio of 1.40.
W = 1.05 / 1.40 = 0.75
The width is 0.75 cm.
FAQ
What is a good length-to-width ratio for a diamond?
A good ratio depends on the diamond shape. Round and square diamonds are usually close to 1.00. Ovals, emeralds, pears, and marquise diamonds usually have higher ratios because they are intentionally elongated. Use the ratio as a shape guide, not as a complete quality grade.
Does a higher L/W ratio mean the diamond is bigger?
No. The L/W ratio describes the outline shape, not the carat weight or total size. Two diamonds can have the same ratio but different carat weights, depths, and face-up measurements.
Can I use millimeter measurements?
The calculator fields support inches, feet, centimeters, and meters. If your diamond measurements are in millimeters, convert them to centimeters by dividing by 10. For example, 10.2 mm is 1.02 cm, and 6.8 mm is 0.68 cm.
