Pyrometric cone temperature converter
Every Orton cone from 022 to 14, adjusted for your cone form, heating rate and hold time. In °F and °C.
Cone and temperature converter
The full chart
All 38 Orton cones, grouped by what people fire them for. Each cell shows both units, with your selected one on top. Blank means Orton publishes nothing for that combination, usually because the cone is not made in that form.
Showing all 38 cones
| Cone | Self-supporting27 °F/hr15 °C/hr | Self-supporting108 °F/hr60 °C/hr | Self-supporting270 °F/hr150 °C/hr | Large108 °F/hr60 °C/hr | Large270 °F/hr150 °C/hr | Small540 °F/hr300 °C/hr |
|---|---|---|---|---|---|---|
| Overglaze, lustre and china paintGold lustre, enamels, china paint and decals fired onto already glazed ware. | ||||||
| 022 | Not published | 1087586 | 1094590 | Not published | Not published | 1166630 |
| 021 | Not published | 1112600 | 1143617 | Not published | Not published | 1189643 |
| 020 | Not published | 1159626 | 1180638 | Not published | Not published | 1231666 |
| 019 | 1213656 | 1252678 | 1283695 | 1249676 | 1279693 | 1333723 |
| 018 | 1267686 | 1319715 | 1353734 | 1314712 | 1350732 | 1386752 |
| 017 | 1301705 | 1360738 | 1405763 | 1357736 | 1402761 | 1443784 |
| 016 | 1368742 | 1422772 | 1465796 | 1416769 | 1461794 | 1517825 |
| Low-fire and early bisqueCool bisque, enamels and some commercial low-fire products. | ||||||
| 015 | 1382750 | 1456791 | 1504818 | 1450788 | 1501816 | 1549843 |
| 014 | 1395757 | 1485807 | 1540838 | 1485807 | 1537836 | 1598870 |
| 013 | 1485807 | 1539837 | 1582861 | 1539837 | 1578859 | 1616880 |
| 012 | 1549843 | 1582861 | 1620882 | 1576858 | 1616880 | 1652900 |
| 011 | 1575857 | 1607875 | 1641894 | 1603873 | 1638892 | 1679915 |
| 010 | 1636891 | 1657903 | 1679915 | 1648898 | 1675913 | 1686919 |
| 09 | 1665907 | 1688920 | 1706930 | 1683917 | 1702928 | 1751955 |
| 08 | 1692922 | 1728942 | 1753956 | 1728942 | 1749954 | 1801983 |
| Earthenware bisque and glazeThe common bisque range and low-fire glaze. Clay stays porous. | ||||||
| 07 | 1764962 | 1789976 | 1809987 | 1783973 | 1805985 | 18461008 |
| 06 | 1798981 | 1828998 | 18551013 | 1823995 | 18521011 | 18731023 |
| 05½ | 18391004 | 18591015 | 18771025 | 18541012 | 18731023 | 19091043 |
| 05 | 18701021 | 18881031 | 19111044 | 18861030 | 19151046 | 19441062 |
| 04 | 19151046 | 19451063 | 19711077 | 19401060 | 19581070 | 20081098 |
| 03 | 19601071 | 19871086 | 20191104 | 19871086 | 20141101 | 20681131 |
| 02 | 19721078 | 20161102 | 20521122 | 20141101 | 20481120 | 20981148 |
| 01 | 19991093 | 20461119 | 20801138 | 20431117 | 20791137 | 21521178 |
| Mid-fire stonewareThe usual studio range. Most commercial stoneware and glazes are formulated for cone 5 to 6. | ||||||
| 1 | 20281109 | 20791137 | 21091154 | 20771136 | 21091154 | 21631184 |
| 2 | 20341112 | 20881142 | 21271164 | 20881142 | 21241162 | 21741190 |
| 3 | 20391115 | 21061152 | 21381170 | 21061152 | 21341168 | 21851196 |
| 4 | 20861141 | 21241162 | 21611183 | 21201160 | 21581181 | 22081209 |
| 5 | 21181159 | 21671186 | 22051207 | 21631184 | 22011205 | 22301221 |
| 5½ | 21331167 | 21971203 | 22371225 | 21941201 | 22331223 | Not published |
| 6 | 21651185 | 22321222 | 22691243 | 22281220 | 22661241 | 22911255 |
| 7 | 21941201 | 22621239 | 22951257 | 22591237 | 22911255 | 23071264 |
| High-fire stoneware and porcelainReduction and gas work, porcelain, salt and soda. Cone 9 to 10 is the classic range. | ||||||
| 8 | 22121211 | 22801249 | 23201271 | 22771247 | 23161269 | 23721300 |
| 9 | 22351224 | 23001260 | 23361280 | 22951257 | 23321278 | 24031317 |
| 10 | 22841251 | 23451285 | 23811305 | 23401282 | 23771303 | 24261330 |
| 11 | 23221272 | 23611294 | 23991315 | 23591293 | 23941312 | 24371336 |
| Technical and refractoryAbove the range of most studio kilns. Industrial and refractory testing. | ||||||
| 12 | 23451285 | 23831306 | 24191326 | 23791304 | 24151324 | 24711355 |
| 13* | 23891309 | 24281331 | 24581348 | 24101321 | 24551346 | Not published |
| 14* | 24641351 | 24891365 | 25231384 | 24911366 | 25301388 | Not published |
No cone matches that. Try 6, 05, or 010.
* Orton notes large cones 13 and 14 use a different composition from the rest of the range. Iron-free cones, recommended for reduction firings between cones 010 and 3, have their own equivalents and are not shown here.
What counts as down
A cone takes roughly 15 to 25 minutes to fall once it starts moving. Every temperature in this tool refers to the last position below: the tip bent level with the base. Not the first slump, and not the tip touching the shelf.
Unfired
Upright. No heat-work yet.
Starting
Softening. It moves slowly at first.
Halfway
Tip horizontal, the 3 o’clock position. From here it goes fast.
Down
Tip level with the base. Every published temperature refers to this position.
How to read these numbers
A pyrometric cone does not measure temperature. It measures heat-work, the combined effect of how hot the kiln got and how long it took to get there. Clay and glaze mature on heat-work too, which is exactly why the industry uses cones instead of thermometers. Two firings that both peak at 2232 °F can produce very different pots if one crawled to temperature and the other sprinted.
Three things move the number
Heating rate over the final 180 °F. Not the average for the whole firing, only the last stretch. A faster climb means a higher bending temperature.
Cone form. Self-supporting, large and small cones bend at measurably different temperatures because of their mounted height and geometry. Mount large cones at 1¾″ instead of 2″ and Orton says to read them against the self-supporting column instead.
Hold time at peak. A cone sitting near its equivalent temperature keeps absorbing heat, keeps forming glass, and keeps bending.
A worked example
Fire a glaze load to cone 6 in an electric kiln with the final segment climbing at about 108 °F/hr. Self-supporting cones give 2232 °F (1222 °C), the number most people quote. Now add a 90 minute hold at peak, common practice for evening out glaze surfaces. By Orton's own rule, a 1 to 2 hour hold delivers enough extra heat-work to bend the next cone up. Your controller still says cone 6, but your ware has effectively been fired to cone 7. If your glaze runs or your clay slumps, that is very often the reason, not a faulty kiln and not a bad recipe.
Where this will mislead you
These are equivalents, not guarantees. Orton determined them in electric kilns in an air atmosphere under controlled conditions. Your kiln is not that kiln. Cones bend over a range of roughly 40 °F, so treat the figure as the centre of a band rather than a threshold.
Reduction and sulfur change things. Reducing atmospheres and sulfur bearing gases affect how a regular cone behaves. For reduction firings between cones 010 and 3, Orton recommends iron-free cones, which have their own equivalents.
The soak rule is a rule of thumb. "One to two hours bends the next cone" is genuinely Orton's guidance, but the real figure depends on cone number, atmosphere and how close to the equivalent temperature you hold. This tool reports it as a step rather than an interpolated number, because interpolating it would be false precision.
Celsius here is converted, not transcribed. The stored values are Orton's published Fahrenheit figures. Orton also publishes a separate Celsius chart whose values differ from a straight conversion by a degree or two due to independent rounding. That gap is well inside the range over which a cone bends, but it is real if you are comparing charts.
Your pyrometer has its own error. Thermocouples drift and age, and they read the air near the tip rather than the temperature of your ware. A cone that disagrees with your controller is usually the one telling the truth. Nothing here replaces witness cones: put them in the kiln, on the shelf, where you can see them.
Terms on the chart
- Heat-work
- The combined effect of temperature and time. What cones measure, and what clay and glaze respond to.
- Temperature equivalent
- The temperature at which a cone bends until its tip is level with its base, under Orton's test conditions at a stated heating rate.
- Witness cone
- A cone placed where it can be seen through a spyhole or inspected afterwards, confirming what the firing actually delivered.
- Calcining
- Pre-firing cones to about 850 °F (455 °C) so trapped binder gases cannot bloat them during a fast firing.
- Soak or hold
- Time spent at peak temperature rather than cooling immediately. Adds heat-work without adding temperature.
Questions potters actually ask
What temperature is cone 6?
For a self-supporting cone at the standard 108 °F/hr rate, cone 6 is 2232 °F (1222 °C). That single number is only true for those conditions. The same cone bends at 2165 °F if you climb slowly at 27 °F/hr, and at 2269 °F if you climb fast at 270 °F/hr, a spread of over 100 °F. A large cone gives 2228 °F and a small cone 2291 °F.
This is why potters who quote "cone 6 is 2232" sometimes get results that do not match their kiln.
Why did my cone not bend even though the pyrometer hit the right temperature?
Because cones do not measure temperature. They measure heat-work, the combined effect of temperature and time. A pyrometer reports the instantaneous air temperature at the tip of its thermocouple. A cone reports how much total heat the ware has actually absorbed.
If you raced to peak, the cone has had less time to absorb heat and will not have bent, even though the controller number looked right. Climb more slowly, or hold at peak, and the same cone will go down.
Which heating rate should I choose?
The rate over the last 180 °F of the firing, not the average for the whole firing. Most electric kilns on a standard glaze program are near 108 °F/hr at the end, which is why that column is the one usually quoted. A slow final segment can be closer to 27 °F/hr, and a fast bisque can approach 270 °F/hr.
If you are not sure, check the last segment of your controller program. That is the number you want.
Does holding at temperature change which cone bends?
Yes, and the effect is large. Orton's published guidance is that a 1 to 2 hour hold is generally enough to also bend the next cone up, and a 4 to 6 hour hold is enough to bend two cones up.
So a firing to cone 5 with a two hour hold delivers roughly cone 6 of heat-work. This is how many potters reach cone 6 maturity without ever showing cone 6 on the controller.
What is the difference between self-supporting, large and small cones?
Height and mounting. Self-supporting cones have a moulded base and stand on their own. Large cones are mounted in a wad of clay at 2″ above the base, and small cones at 15/16″. Because the bending geometry differs, each form has its own temperature equivalents.
One gotcha catches people constantly. If you mount large cones at 1¾″ rather than 2″, Orton says to read them against the self-supporting temperatures instead.
Should I use iron-free cones?
Orton recommends iron-free cones for all reduction firings between cones 010 and 3. Reducing atmospheres and sulfur oxides affect how a regular cone behaves, so an iron-free cone gives a more reliable reading in gas, wood and soda kilns in that range. They have their own published equivalents, which differ from the regular figures by up to about 40 °F.
How far does a cone bend before it counts as down?
The published temperature equivalent is the point at which the cone tip has bent level with its base. That is the reference position for every number on the chart.
Once a cone starts moving it typically takes 15 to 25 minutes to finish. It bends slowly at first, then quickly after it passes the halfway (3 o'clock) point. The difference between a cone touching the shelf and one at 4 o'clock is only a degree or two, so do not agonise over the last bit of droop.
Can I fire cones without pre-firing them?
Usually yes, but not in a fast firing. If a cone is heated too quickly its surface fuses before the binders inside have burned out, and the trapped gases bloat the cone and ruin the reading. For rapid firings Orton advises calcining cones first, meaning pre-firing them to about 850 °F (455 °C) in an air atmosphere.
Where these figures come from
Temperature equivalents are transcribed from Temperature Equivalent Chart for Orton Pyrometric Cones (°F), Cone Numbers 022 to 14, published by The Edward Orton Jr. Ceramic Foundation. Guidance on bending behaviour, soaking, iron-free cones, calcining and mounted heights comes from the notes printed on that same chart.
Orton publishes current charts and further reference material atortonceramic.com. If you are firing something that matters, check your figures against their current publication. This tool is a convenience. They are the authority.