How to Calculate the Weight of a Diamond Without Scales

Introduction to estimating diamond weight without scales

This article explains how to determine the weight of a diamond without using scales.

Normally, diamond merchants use accurate diamond scales to weigh diamonds—measured to three decimal places or a thousandth of a carat. However, scales may not always be available, such as when a diamond is already in a ring.

We can use specialized formulas to estimate the diamond’s weight in such cases. We use different formulas for different diamond shapes, such as round or marquise. These formulas rely on measurements of the diamond, such as its width and depth, to estimate its weight.

Importance of knowing the weight of a diamond

It is important to note that these formulas provide an approximate weight, not an exact one. Therefore, verifying the weight using scales whenever possible is always advisable, particularly when diamonds are being traded between parties.

Using formulas to weigh a diamond without scales

These formulas may be beneficial when a diamond is already set in jewellery, such as an engagement ring. If we cannot remove the diamond from the setting to weigh it, we can still apply the formulas to estimate its weight.

Special instruments used to measure diamonds

We can use a specialized tool called a Presidium Diamond Gauge to measure the diamond’s diameter and depth, which we can then use to apply the formulas.

The Presidium gauge is used to measure diamonds from small melee stones to large single stones.

Adjustments needed when using formulas to estimate diamond weight

When using these formulas, several factors must be considered. For instance, adjustments may be necessary for the diamond’s girdle thickness (the part around the edge of the diamond) and pavilion bulge (the part at the bottom of the diamond), as well as for different diamond shapes.

When to use formulas to estimate diamond weight

Overall, formulas can be a useful tool for estimating the weight of a diamond in certain circumstances. Nevertheless, it is essential to remember that these estimates are less accurate than weight measurements taken with a scale. Therefore, weighing the diamond on a scale is the best method for obtaining a precise weight whenever possible.

4 Formulae for approximating the weight of diamonds

Round Brilliant Cut Diamonds

Carats = Diameter² x Depth x 0.00609664

Pear Shaped Diamonds

Carats = 0.0059136 x Length x Width x Depth

Marquise Cut Diamonds

Carats = 0.055651 x Length x Width x Depth

Square Diamonds (Includes Emerald Cuts / Princess / Carré)

Carats = 0.0088563 x Length x Width x Depth

If you happen to have one or more diamonds and want to estimate their weight without using a scale, taking some measurements and applying the appropriate formula can provide a fairly accurate result. However, remember that these calculations provide estimates and not exact weights. For this reason, double-check weights with a scale, especially in situations where the value of the diamond is high, such as in trading or appraising.

Mathematical formulae provide useful guidance when a diamond’s depth is difficult to measure or is already set in jewellery, and the formula can estimate the diamond’s depth.

Nevertheless, it’s important to note that the results of this method are also approximations and not as precise as using a scale. So, it’s always best to verify with a scale whenever possible to ensure a diamond’s most accurate weight and measurements.