Wastage = Gross gold weight – Net pure gold weight
Net pure gold weight = Gross gold weight × Purity percentage
Wastage percentage = (Wastage ÷ Gross gold weight) × 100
If purity is given in karats, Purity percentage = Karat ÷ 24
Pure gold content = Gold item weight × (Karat ÷ 24)
Wastage in grams = Total gold used – Pure gold recovered
Making loss can be added to wastage if required
Total cost with wastage = Gold weight × Rate per gram + Making charges + Wastage cost
Wastage cost = Wastage weight × Gold rate per gram