Briolette stone weight estimation

Hi, Orchid! Does anyone know any formulae for estimating the carat
weight of briolette cut stones? We’re getting pieces in to appraise
with briolettes, and I’m not sure how to estimate, other than
finding similarly cut gems of the same type and weighing them…

Thanks in advance!
Jenny Sweaney

Mardon Jewelers
3640 Main Street
Riverside, CA 92501