Pyrometric Cone Temperature Calculator (Orton Cones vs Heating Rate, °C & °F)

How it works

end-point interpolated on log(rate) between the Orton 60 °C/h and 150 °C/h columns · hold equivalence ≈ 0.5 °C per minute at peak (30 min ≈ ½ cone) · °F = °C × 9/5 + 32

A pyrometric cone bends when it has absorbed a certain amount of heat-work — a combination of how hot and for how long. That is why the same cone is listed at different temperatures for different heating rates: fire slowly and it falls at a lower temperature; fire fast and it needs more. A digital controller reads temperature only, so the cone in the kiln is the true judge of whether your glaze matured. Use this calculator to set a controller target that matches the cone at your actual final ramp rate, to understand what a hold does, and to choose the three-cone witness pack that tells you whether the firing was under, on, or over.

Worked example

Cone 6 fired with a 60 °C/h final ramp bends at about 1,222 °C (2,232 °F); at 150 °C/h it needs about 1,243 °C. Adding a 15-minute hold at peak supplies roughly 8 °C of extra heat-work, so a controller set to about 1,214 °C with the hold gives the same cone 6 result. The witness pack is cone 5 (guide, fully down), cone 6 (target) and cone 7 (guard, barely bending).

Frequently asked questions