When measuring a triangular diamond, the width is the narrowest side (point to point), and the length is measured from the narrowest side to the opposite point.

Width: 6.96 mm
Depth: 4.04 mm
Girdle: Very Thick
Shape: NA

Formula would read:

7.89 x 6.96 x 4.04 x .0057 x 1.045 (GTA) = 1.322 Rounded to 1.32 ct.

The important point to remember is to always take a somewhat conservative approach when buying but not too much so. As mentioned earlier, if your weight estimation is substantially in your favor it will make you appear dishonest and/or unprofessional. Take your time and be careful. With time and experience weight estimations will measuring a triangular diamond, the width is the narrowest side (point to point), and the length is measured from the narrowest side to the opposite point.

Triangular Brilliant Formula: Length x Width x Depth x .0057 x GTA x Shape Adjustment

Example:

Length: 6.32 mm
Width: 6.02 mm
Depth: 2.52 mm
Girdle: Thick
Shape: NA

Formula would read:

6.32 x 6.02 x 2.52 x .0057 x 1.03 (GTA) = 0.5629 Rounded to 0.56 ct. become second nature.