Kiln Loading Calculator (Pieces per Shelf, Shelf Levels, Posts & Load Capacity)

How it works

pitch = footprint + gap; round shelf: pieces ≈ 0.78 × (usable diameter ÷ pitch)²; rectangular: floor(W/pitch) × floor(D/pitch) · post = next standard size ≥ piece height + clearance; level = post + shelf thickness; levels = floor((H − first posts − shelf) ÷ level) + 1

A kiln load is a stack of shelf levels, each holding as many pieces as the footprint and spacing allow, separated by posts tall enough to clear the pieces beneath. Glazed pots need air around them so glaze cannot bridge, and a little clearance so nothing touches the shelf above; bisque can be packed tight and stacked. This calculator turns your kiln's interior dimensions and a typical piece size into the number of levels, posts and shelves you need and the pieces a full load holds — handy for pricing kiln time, planning production, or deciding whether that big platter is worth firing alone.

Worked example

A 58 cm-wide, 69 cm-tall octagonal top-loader (≈ 5.9 cu ft) glaze-firing 9 cm mugs 10 cm tall with a 1.5 cm gap holds about 21 mugs per shelf pair; with 12.5 cm posts and 1.6 cm shelves each level takes 14.1 cm, giving 4 levels — about 84 mugs per load using 12 posts and 8 half-shelves, with about 11 cm of height left over for a level of short pieces.

Frequently asked questions