Coil Pot Calculator

Building a coil pot means stacking rolled ropes of clay in rings until you reach the target height, and this calculator works out how much rope you'll need before you start rolling. It first finds the circumference at the wall's centerline — the pot diameter minus the wall thickness, times pi — since coils sit roughly in the middle of the finished wall, not at its outer edge. Because a rolled coil flattens and spreads when pressed onto the row below, the calculator assumes each coil's effective stacked height is only about 80% of its rolled diameter, then divides your target pot height by that compressed height to get the number of rows, rounding up. Multiplying rows by the centerline circumference gives the total wall coil length.

For the base, it approximates a spiral of coil filling a circular disk by dividing the base's area by the coil's diameter — a standard shortcut for estimating Archimedean spiral length, though it can undercount slightly for very tightly wound spirals. Wall and base coil lengths together give a grand total in feet. To estimate clay weight, it takes the coil's cross-sectional area (pi times the radius squared) times the total combined length to get wet clay volume in cubic inches, then multiplies by an assumed wet clay density of about 0.065 lbs per cubic inch. Because that density and the spiral shortcut are approximations, treat the clay weight as a wedge-up-a-bit-extra estimate rather than an exact material order, and always keep spare clay on hand for a coil pot build.