Pyrometric Cone Temperature Converter
Cones measure heat work, not just temperature — which is why the same cone bends at different readings depending on how fast you fire. Look up any cone in °F and °C at two standard rates, or find the nearest cone to a target temperature.
Most electric studio firings ramp slowly at the end; faster schedules need a higher temperature for the same cone.
How cones work
A pyrometric cone is a shaped ceramic mixture that softens and bends when it has absorbed a specific amount of heat work — the combined effect of temperature and time. The listed temperature is where it bends at a stated heating rate, not a fixed melting point.
Cone numbering runs in two series. Numbers with a leading zero (022 up to 01) go from coolest to hotter, then the plain series continues (1 through 12) hotter still. Fahrenheit converts with °C = (°F − 32) × 5⁄9.
Worked example
Cone 6, a common mid-range stoneware target, bends near 2232 °F (1222 °C) at the slow rate but around 2269 °F (1243 °C) if you fire fast. Cone 04, typical for bisque, sits far lower at about 1945 °F (1063 °C) — and note it is nothing like cone 4 at roughly 2124 °F.
Firing by cone
Heat work, not temperature
A kiln controller reads temperature, but clay and glaze respond to how long they spend hot as well as how hot they get. Holding just below a target can mature a body as thoroughly as pushing higher briefly. Cones capture that combined effect, which is why potters trust them over a thermocouple reading alone.
Mind the leading zero
The two numbering series confuse almost everyone at first. Cone 04 and cone 4 are nearly 180 °F apart, and firing a low-fire body to the wrong one can slump work onto the shelf. Reading the zero carefully on glaze labels and clay datasheets prevents an expensive kiln load.
Use witness cones
Even a well-calibrated controller drifts as elements age, and kilns fire unevenly top to bottom. Placing witness cones on each shelf shows what actually happened where the work sat, and it is the quickest way to spot a failing element or a thermocouple that needs replacing.