This chart intended to provide a good indication within a reasonable tolerance.
Left column is material converting from.
Convert wax to metal
wax model weight x factor of metal wanted = weight of metal wanted
example: 1.5 grams wax x 10.40 (sterling silver factor) = 15.6 grams sterling silver
Convert metal to metal wanted
model weight in metal x factor of metal wanted = weight of metal wanted
example: 6.0 grams sterling silver x 1.25 (14kt factor) = 7.5 grams 14kt gold