Hi David,

It's very hard to estimate the volume of the final mix for hypertufa since some of the ingredients are irregular shapes and absorb liquids unpredictably. You can mix all the dry ingredients without water - that'll give you roughly the volume you need. I recently tried to make some pots and ended up grossly underestimating how much mix I needed. Bear in mind that if your molds have any give to them they'll also eat up much more mix than you expect. If it's really important to you not to have too much spare material, you can use the volume of your mold times the density of concrete to get a conservative estimate of the weight of material needed.