How much silicone is needed to fill a mold box

A mold box may be a glass or plastic container, a milk carton or constructed from Styrofoam, wood, metal, Lego blocks, glass or acrylic sheets. 

Measure the box dimensions with a tape measure to calculate the volume of silicone required to make your mold. First, the box size should allow for 1/2” clearance over the top and all sides of the model. The formula for determining the required volume is: V=WxDxH 

V = volume in cubic inches 
W= width 
D= depth (front to back) 
H= Height 

Multiply your dimensions to get the total volume in cubic inches. Divide this number by 25 (the cubic inches of LiquaFast-Ice per pound) to give you the  number of pounds of resin to fill the box.  

This formula can also be used to determine the volume of resin required to make a 2 part mold.

Make your dimension measurements for the first pour after you have laid  a clay base, then do the same for the second pour after the clay has been removed (with the model half-way embedded in the cured resin). Add the resin required   for both pours to give you the total volume required to make your 2-part mold.
  
A helpful hint for you is to make several different size and shaped pouring gates for later use. A preformed, hardened pouring gate when placed in the second mold half prior to pouring will eliminate the need for cutting in the gate later. Making a gate is easy. Just roll several size funnel shapes out of an air drying clay such as Das Pronto, Kneadatite or an oven drying Sculpey. Sand off any irregularities.