How to choose a method
Per piece is the simplest to explain and to run at the counter. It undercharges big pots and overcharges small ones, so most studios add a size cap.
Per cubic inch follows the shelf space a piece takes. It is the fairest for mixed work, but needs a ruler and a little math, which is what this calculator does for you.
By weight is quick if you already have a scale. It undercharges tall, light forms that eat shelf space, such as vases and bottles.
Why a minimum matters
A single small cup still costs you a shelf slot, a cone and your time to load and unload. A minimum per firing keeps tiny loads from losing money.
Pro tip
Test your rates against five typical members. If light users pay the minimum and heavy users pay well above it, the rate is working. Adjust until your average load covers electricity, kiln wear and labor. The default numbers here are placeholders, not recommendations.