Forge Temperature Calculator by Steel Type
Static heat-colour charts treat all steel the same. Pick your steel type to get the recommended forging colour range and a clear "do not exceed" warning, alongside the full standard reference chart. Nothing uploaded.
Recommendation
Heat Colour Reference Chart
| Colour | °C | °F | Meaning |
|---|
Learn more: reading forge colour by steel type
What each colour band covers
The chart on this page is the standard published heat-colour reference. It starts at black with no glow below 480°C (900°F), then runs through dark red at 580-650°C (1070-1200°F), red at 650-750°C, and cherry red at 750-850°C (1380-1560°F).
Above that sit the working colours: orange at 900-1000°C (1650-1830°F), yellow at 1000-1100°C, light yellow/white at 1100-1300°C, and white above 1300°C (2370°F). White is where the chart stops giving an upper bound, because that is where most carbon steels risk burning.
The table is not continuous. Cherry red tops out at 850°C and orange does not begin until 900°C, so a glow sitting between the two does not land on a band at all. That gap comes from the published reference itself, not from rounding done here.
Two of the cooler bands are labelled for what they are not good for. Dark red is marked too cold to forge most steel, and red is described as the upper end of the tempering and annealing range rather than a forging heat.
Why each steel type gets a different range
Mild and low carbon steel is recommended across orange through yellow, 900-1100°C. It can approach light yellow/white for forge welding, and the warning attached to it is about prolonged time above that point rather than touching it briefly.
Medium carbon steel has the narrowest recommendation of the four, a single band. Orange only, 900-1000°C, with yellow and above flagged for grain growth that weakens the finished piece.
High carbon and tool steel also gets two bands, cherry red and orange, but it starts lower than the others at 750°C. Yellow and above is the hard line: the surface burns and decarburizes, which is what costs the steel its edge holding.
Stainless sits in the same orange-to-yellow window as mild steel for unrelated reasons. It work-hardens quickly and conducts heat differently from carbon steel, and pushing it past its range causes scaling and lost corrosion resistance instead of a lost edge.
The do-not-exceed warning follows one rule. It fires when the colour you picked sits higher in the chart than the top of that steel's recommended bands. Nothing about a specific alloy or the thickness of your stock feeds into that check.
Forge welding needs a different chart than ordinary forging
A forge welding temperature chart and a forging temperature chart aren't the same thing. Forging just needs the steel soft enough to move under the hammer, which for most carbon steel means the orange-to-yellow bands, 900-1100°C. Forge welding needs the surfaces hot enough to actually fuse, which pushes into light yellow/white, 1100-1300°C, the band this tool's colour table marks as welding heat.
That's why mild steel's recommended range here tops out higher than medium or high carbon steel's does: it's the one family flagged as able to approach light yellow/white for forge welding without excessive risk. Medium and high carbon steel are capped at orange because pushing them to welding heat burns the surface before you get there.
Lighting changes what you see
The same bar at the same real temperature reads cooler in bright daylight than in a dim shop, because judging colour is a contrast judgement against whatever light is already in the room. Working under low, steady light gives you a reference point you can repeat tomorrow.
Dragon's Breath Forge says the same thing in its introduction to bladesmithing: "judging the temp by color is affected by ambient light", and its suggested fix is to confirm with a magnet rather than trust the eye alone. That page also notes that the higher the carbon and alloy content, the more sensitive a steel is to being worked in the correct range, which matches the lower ceiling this tool puts on high carbon and tool steel.
FAQ
Which steel type has the narrowest range in this tool?
Medium carbon steel. It is the only one recommended for a single colour band, orange at 900-1000°C, with yellow and above flagged for grain growth. High carbon and tool steel gets two bands but starts lower, at cherry red.
Does this account for a specific alloy like 1084 or O1?
No. The tool covers four broad families: mild and low carbon, medium carbon, high carbon and tool steel, and stainless. It holds no per-alloy compositions, so for a named grade check the forging range your supplier publishes for it.
Can I use colour instead of a thermometer?
Colour is a working estimate rather than a measurement. Ambient light and your own eyes both shift the read, so treat every band here as a range to aim at, and confirm with an instrument when the job depends on hitting it.