Diamond Pavilion Angle: Complete Guide and Calculation

Diamond Pavilion Angle: Complete Guide and Calculation

Diamond Pavilion Angle: Complete Guide and Calculation

Posted by Sharif Khan on 11th Mar 2020

Have you ever bought a diamond as a present for that special person in your life? Probably, you took the time to go through websites and resources online that talk about the best kind of diamond. If you’re still a novice in the world of diamonds, the jargon and calculations can make you want to throw in the towel. The good news is that we have your back.

In this article, we will walk you through the meaning of the diamond pavilion angle, how to calculate it using simple mathematics, and how to determine the ideal one.

What is a diamond pavilion angle?

First, what is a diamond pavilion? In its simplest definition, a pavilion is a diamond’s bottom half, hidden under a ring arrangement. It is a very crucial part of this precious metal’s general appearance. Why? It has facets which assist in light reflection, penetration, and bouncing. The result is fire and brilliance.

The Pavilion consists of three parts, namely the Culet, the Girdle, and the Pavilion Facets.

  • Girdle - the outermost edge of the metal
  • Pavilion facets - the part which slopes between the culet and the Girdle
  • Culet - the meeting point of the sloping pavilion facets.

Therefore, the Pavilion Angle is the pavilion facets’ angle in relationship to the plane of the Girdle.

James Allen

The effects of the Pavilion on the diamond’s sparkle

The shining and sparkling nature of the metal relies heavily on the Pavilion. When you shine light through a diamond, it passes through the table and crown. Once it reaches the Pavilion, the light will bounce and sparkle through the metal. The pavilion angle will determine how the refraction and sparkling occur.

Too shallow pavilions will give a “fisheye” effect because of Girdle’s reflection in the table. Not satisfying results. The light going perpendicularly through the crown will bend too much. It will not refract across the opposite pavilion facet. Instead, it will jump off the crown facet at the opposite and exit the stone through the second pavilion facet. In simple terms, it will go through the gem and leak out through the bottom.

On the other hand, if your diamond has too deep Pavilion, the table surface will look darker and create an impression of a “nail head.” That’s not what we want in a diamond. Here is what happens. The light will bounce at a shallow point, and it will again leak out from the bottom near the culet. That’s because the perpendicular light going through the table and crown facet will not be steep enough to bounce well at the first pavilion facet. Consequently, the opposite Pavilion facet will not correctly reflect the light.

For an ideal angle, the light goes through the crown facet and bounces off the first pavilion facet. The light will proceed to the opposite pavilion facet and bounce again. The light will eventually leak off through either the second crown facet or table facet and return to the observer. A perfect combination of pavilion and crown facets will give an excellent equilibrium between the fire and brightness while cutting down unwanted leakage of light.

Ideal Pavilion angles

According to Marcel Tolkowsky’s calculations, 40.75 degrees is the perfect pavilion angle of a diamond. Surprisingly, before scientists determined this angle mathematically, cutters were achieving it. For ages, the cutters have been agreeing that above 41 degrees are too deep.

Sellers of poorly cut stones will argue that it’s laughable to have a diamond with 41 degrees slope. However, it is a fact that light leaks beyond a particular critical angle. In reality, what occurs is not too much cliff, but a seamless change from stronger to weaker reflections as leakage increases. What you need to remember is that this transition happens at around 41 degrees. Therefore, something nearer to 40.75 degrees is satisfying, unless you want an ideal stone with 40.9 degrees.

Most studies have concluded that angles below 40.5 degrees are too shallow and will result in light leakages and obstructions. The Gemological Institute of America (GIA) always round off the 40.5 degrees angle to 40.6 in their reports. Therefore, we arrive at an acceptable pavilion angles range of 40.6- 41 degrees.


How to calculate the Pavilion angle

The mathematics behind calculations of this all so important angle is not as hard as it appears. First, you must know the following:

  • Crown depth
  • Pavilion depth
  • Table

All of these dimensions are usually in % of the average diameter.

Now, follow the following steps:

  • Take out your calculator and enter the Pavilion depth
  • Then divide the pavilion depth by 50
  • After that, calculate the Tan Inverse (Tan-1). Don’t worry.

Simply hit the Tan-1 button on your calculator.

If you don’t have the Tan-1 button, do this instead:

  • Locate the symbol Tan-1 written above the Tan button.

Hit the shift, then Tan buttons.

Voila! You’ve found the Pavilion Angle.

An example will do:

Pavilion depth= 42.9 %

Therefore, 42.9÷ 50= 0.858

The Tan-1 of 0.858 = 40.63 degrees

As simple as that!

As we have seen above, apart from the pavilion Angle, the other dimensions are also critical. An experienced diamond cutter will know how to relate them proportionately to come up with a stunning gem.

A super excellent round cut diamond will have the following ranges:

  • Depth= 61%- 62.5%
  • Pavilion Angle= 40.6%- 41%
  • Table size= 54%- 57%
  • Crown angle= 34%- 35%
  • Girdle Thickness= Thin- Medium
  • Culet= None


An ideal pavilion angle is hugely responsible for the lovely and beautiful appearance we see in polished diamonds. The angle refracts light from one facet to another and then reflects it to you through the table. Your diamond will not have that stunning look if it lacks that perfect Pavilion.

When doing your shopping, be careful not to fall for poorly cut diamonds. Is the diamond’s pavilion depth, pavilion angle, and other dimensions falling within the perfect ranges? The good news is that you now know how to calculate these dimensions. These seemingly minute details are what bring the big difference between ideal and poorly cut diamonds.

Now you have the information. Go ahead and confidently do the shopping.