Clay Weight Calculator

In short How much clay a pot needs is geometry: a cylindrical form is a ring of wall plus a disc of base, and the clay is the volume of those two multiplied by the density of wet clay. A 10 cm pot 12 cm tall with a 6 mm wall and a 10 mm base works out at 273 cm³, which at about 1.9 grams per cubic centimetre is roughly 520 grams. THE BASE IS A BIGGER SHARE THAN PEOPLE EXPECT. In that example the wall is 195 cm³ and the base 79 — nearly a third of the clay in a part nobody sees. A base thrown twice as thick as it needs to be wastes clay, takes far longer to dry, and is the commonest cause of an S-crack. This is the clay in the finished form rather than the ball you start with, so add ten to twenty per cent for what goes on the wings, into the trimmings and down the slop bucket. Weighing out at all — rather than pulling a lump off by eye — is the single fastest route to a set of mugs that match, and the number this page gives you is the one to weigh. AND THE CAPACITY IS WHERE THE SURPRISE IS. That form holds about 669 ml wet. Fire it in a body shrinking 12% linearly and it holds 456 ml, because all three dimensions shrink and volume falls by the CUBE of the linear figure. A mug thrown to hold a comfortable mugful usually is not one, which is why potters who care about capacity throw a test piece and measure the fired result rather than the wet one. If you tick the finished-size box, the page scales every dimension up before doing the geometry — including the wall thickness, which shrinks too and which people almost always forget. One convention and one limit. The density of wet clay is taken as 1.9 g/cm³ and it varies with body and water content; weigh a known ball once and you will have your own figure. And this is a cylinder — a bellied form, a bowl or anything thrown with a curve holds and weighs differently, so treat the answer as a starting weight rather than a specification.