Cone & Kiln Temperature Converter

Every cone number tells your kiln exactly how much heat to give a piece — not just how hot to get, but how long to hold it there. This tool turns that cone number into a real temperature, so you always know what to aim for.

Pick a cone and firing speed to see it in both °F and °C, or switch to Quick Convert to flip any temperature between the two scales.

What a cone number actually measures

A pyrometric cone is a small, tapered piece of ceramic formulated to bend at a specific amount of heatwork — the combined effect of temperature and time. That's different from a plain thermometer reading, which only tells you the temperature at one instant.

Two firings can hit the exact same peak temperature and still leave a glaze under-fired or over-fired, because one climbed there quickly and the other lingered. Cones — and this converter — account for that by giving two numbers for every cone: one for a medium firing speed, one for a faster one.

Medium vs. fast: which do I use?

Medium (108°F/hr · 60°C/hr) — the more common rate for most home and studio electric kiln firings.
Fast (270°F/hr · 150°C/hr) — suits a quicker schedule, like a rushed bisque or a kiln programmed with a steep climb near the end.

If you're not sure which applies to you, check your controller's ramp rate for the last 180°F (100°C) of the firing — that's the part that matters, not the average across the whole cycle.

A quick guide to common cones

Cone 06–04 — most bisque firings, and the typical earthenware glaze range
Cone 5–6 — the most common mid-fire glaze range for electric kilns
Cone 9–10 — high-fire stoneware and porcelain, often fired in reduction

Frequently asked

Why does my kiln's display show a different number than the chart? Your kiln's thermocouple measures temperature only — it has no idea how fast you got there. Two kilns can both read "1,222°F" and still have delivered different amounts of heatwork. That's exactly why potters keep using physical cones alongside a digital readout: the cone confirms what the ware actually experienced, not just what the sensor reports.

Do I still need real, physical cones if I already have a digital controller? If you want certainty, yes. A controller's sensor can drift, or simply sit in a different spot in the kiln than your work. A witness cone placed next to your pieces is the only thing that tells you what temperature they actually reached.

My glaze recipe lists a Seger cone number that doesn't match this chart. This chart uses Orton cone numbers, the standard across North America and the UK. Seger cones (more common in parts of Europe and Asia) don't line up one-to-one with Orton numbers — as a rough example, a Seger Cone 9 is closer to an Orton Cone 12. Check with your glaze supplier before assuming the two systems match.

Does the cone type — self-supporting vs. large — change the temperature? Only slightly. This chart uses Orton's self-supporting cone data, the type most studios reach for since it doesn't need a plaque to stay upright. Large cones fired at the same rate mature within a degree or two of the same figure, so it rarely matters in practice.

One thing to keep in mind

This chart is a reference, not a guarantee. Kiln hot spots, shelf placement, load size, and your specific clay or glaze can all shift how a firing behaves. Treat these numbers as your starting point, and let a physical witness cone have the final word.

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