L/W Ratio For Gem Cutting: What Is It and How To Use It?

There’s a popular term that circulates in the exciting world of gemstone cutting, and it’s called “L/W.” However, if you’ve ever measured anything, you are apt to have familiarity with this term. So, what does LW ratio mean and how do gem cutters use it?

Not only will we get to the long and short of it in this article, but we’ll help you out with technical tips for how to use L/W ratios to optimize each and every cut.

Ready to cut into this faceting (and fascinating!) technique? Here’s everything you need to know about the L/W ratio in gem cutting.

What is L/W?

As you may have already guessed, L/W is an acronym denoting “length-to-width.” Outside of the world of gemstone cutting, people from all walks of life depend on L/W measurements to measure all sorts of things—from design elements to window treatments, industrial building plans to computing mathematical equations. If you use your imagination, you’ll notice that the world around you is essentially broken down into length-to-width measurements.

Gem cutters, (also known as Lapidaries) use L/W to calculate the precise mathematical ratio required to:

• Cut patterns
• Create custom gemstone designs
• Measure gemstones

Cutting gemstones from rough specimens is the foundation of every Lapidary, which is why proficiency in working with L/W measurements and ratios is vital. First, you need an understanding of why length-to-width is important, which we’ve outlined above. Now, let’s breakdown exactly how the L/W ratio works when put to practice.

What is the L/W Ratio?

While “L/W” means length-to-width, an L/W ratio is the actual mathematical figure required to cut gemstones into popular designs. To compute the L/W ratio for cutting a gem, you’ll have to take millimeter measurements of the length and width of the rough specimen. Once you have these metrics, the equation is simple:

• First, divide the length of the gemstone by its width
• Next, you’re done!

Now, wasn’t that easy? Don’t be intimidated by the variety of numbers you will get. When working with things on the tiny scale of millimeters, it’s common to produce figures such as 1.67. Here’s an example:

Say the length of the gemstone is 8mm and the width is 6mm. Divide 8 by 6 and you end up with 1.33. Just like that, you’ve got your L/W ratio. Now, what can you do with it? Excellent question!

Choosing Gems To Cut with L/W Ratio

Knowing the L/W Ratio of a gemstone helps cutters conceptualize what they’ll be working with. You might think you’ll use the L/W ratio to cut into big, rough specimens, however, this isn’t always the case. More commonly, you’ll choose a gemstone design based on the L/W ratio of the gemstone you want to create.

Here are some helpful guidelines for choosing gemstone designs according to the L/W ratio:

• Choose designs that have a standard L/W ratio
• Always choose a design with a ratio that is smaller than your L/W ratio
• Or, choose a design with an equal L/W ratio to your rough specimen

Think of it this way: you can always trim down excess materials to accommodate a smaller L/W ratio, but you cannot add materials to size up to your ratio. Make sense?

Of course, metrics can be as vast as the gemstones themselves, which is why it helps to understand the standard, and non-standard, L/W ratios. After all, you will likely work with a mix of the two as you create innovative designs and work with common ones.

The Most Standard L/W Ratios

When you work with gemstone designs, you’ll find that the metrics fall in line with standard L/W ratios. If they don’t, you’ll have to create a non-standard design, which we’ll discuss further below. Keep in mind the purpose of each measurement:

• Ratio, as mentioned, specifies the length of a gem divided by its width.
• Width refers to the length of the gemstone divided by its ratio.
• Length equals the width of the gemstone multiplied by its ratio.

The standard L/W ratio falls into three categories: Ovals and rectangles, marquise and pear. Let’s have a look at each one!

Oval and Rectangle

If you’ve browsed any gemstone or jewelry shop, you know firsthand how popular rectangle and oval gemstones are. As such, you’ll want to familiarize yourself with the standard L/W ratios, which are:

• 3x5 = 1.67
• 4x6 = 1.50
• 5x7 = 1.40
• 6x8 = 1.33
• 7x9 = 1.29
• 8x10 = 1.25
• 10x14 = 1.40
• 12x16 = 1.33

Marquise

Another popular gemstone cut is the elegant marquise shape, which typically has a smaller L/W ratio than ovals, rectangles, and pears. Due to its unique shape, most L/W ratios are the same, with the exception of a 3x5 length-to-width.

• 2x4 = 2.0
• 2.5x5 = 2.0
• 3x5 = 1.67
• 3x6 = 2.0
• 4x8 = 2.0
• 5x10 = 2.0
• 6x12 = 2.0
• 7x14 = 2.0

Pear

Who doesn’t love a pair of pears? Well, probably best to start with an L/W ratio of one gem, but you can easily use the L/W ratio to make a pair of pear gemstones. Here are the standard ratios for pear cut gemstones:

• 3x5 = 1.67
• 4x6 = 1.50
• 5x7 = 1.40
• 5x8 = 1.60
• 6x9 = 1.50
• 7x10 = 1.43

What About Non-Standard Ratios?

Glad you asked! Unlike standard L/W ratios, you’ll have to customize a setting for non-standard L/W ratios. The reason being that the standard ratios encompass all of the most popular gemstone cuts and settings. In other words, with standards, you can guarantee that most jewelers and designers carry settings just waiting to hold your gemstone.

Still, there’s a great market for non-standard L/W ratios, and that’s for those who want something entirely original and one-of-a-kind. Keep in mind that it’ll require more work up front, but the final result will be a gemstone unlike any other!

SHOP FOR FACETING ROUGH