How do i figure out how much Silicone Rubber to buy? Monica P. February 26, 2020 16:54 One cubic inch of space requires one ounce of rubber. Related articles Which silicone do you recommend for doing large molds? Which silicone do you recommend for smaller molds? How long does it take for Fiber Lok rug backing to dry? EasyCast Resin Jewelry by Marie Browning Comments 0 comments Article is closed for comments.