Estimating Diamond Carat Weight for Princess Cut Diamonds

Question
Dear Mr. Lumetta
I bought a pair of small princess cut diamond earrings for my little girl. They measure 3mm x 3mm. How does one estimate carat if diamonds are not round?
Thanking you in advance for your time.
V Stein

Answer
HI V. STEIN,

THERE ARE FORMULAS FOR DIAMOND WEIGHT FOR DIFFERENT SHAPES. FOR A PRINCESS OR EMERALD CUT  IT IS LENGTH X WIDTH X DEPTH X .0061 OR .0062 DEPENDING ON THE THICKNESS OF THE GIRDLE AND THE BOWING OF THE PAVILLION. IF IT HAS A HEAVY BOTTOM THEM YOU NEED TO GO TO THE HIGHER NUMBER. I ESTIMATE YOUR 3MM PRINCESS CUTS TO BE .104 TO .112 EACH. I ESTIMATED THE DEPTH AT 1.8MM SINCE THAT IS THE NORM FOR THIS DIAMETER. ACTUAL WEIGHT SHOULD BE WITHIN 5% OF THESE WEIGHTS.

OTHER SHAPES HAVE DIFFERENT FORMULAS TO ESTIMATE WEIGHT.

PETER