Type K thermocouple — colour codes, ranges and tolerances
For Type K thermocouple, positive-leg alloy is Chromel; negative-leg alloy is Alumel; ansi/astm positive-leg color is Yellow; ansi/astm negative-leg color is Red; ansi extension-grade jacket color is Yellow; source document is ANSI/ASTM Thermocouple Color Codes, verified against its source on 2026-08-19.
- Type letter
- K verified
- Positive-leg alloy
- Chromel verified
- Negative-leg alloy
- Alumel verified
- ANSI/ASTM positive-leg color
- Yellow verified
- ANSI/ASTM negative-leg color
- Red verified
- ANSI extension-grade jacket color
- Yellow verified
- Source document
- ANSI/ASTM Thermocouple Color Codes
- ANSI and IEC Color Codes per assets.omega.com
- Thermocouple Tolerances per tc-inc.com
- Thermocouple Colour Code Standards per tc.co.uk
- Usable temperature range
- –270 to 1372°C per assets.omega.com
- IEC 60584 Class 1 tolerance
- –40°C to +375°C ±1.5°C 375°C to 1000°C ±0.004 ⋅ |t| per tc-inc.com
- IEC 60584 Class 2 tolerance
- –40°C to +333°C ±2.5°C 333°C to 1200°C ±0.0075 ⋅ |t| per tc-inc.com
- IEC 60584-3 positive-leg color
- Green per tc.co.uk
- IEC 60584-3 negative-leg color
- White per tc.co.uk
- IEC 60584-3 outer sheath colour
- Green per tc.co.uk
What the source says
Type | Positive conductor | Negative conductor | Positive color | Negative color | Extension-grade jacket | Thermocouple-grade jacket shown in legacy assets | T | Copper | Constantan | Blue | Red | Blue | Brown | J | Iron | Constantan | White | Red | Black | Brown | E | Chromel | Constantan | Purple | Red | Purple | Brown | K | Chromel | Alumel | Yellow | Red | Yellow | Brown |
— thermometricscorp.com, retrieved 2026-08-19
What assets.omega.com says
ALOMEGA ® Clean Oxidizing and Inert. + + CHROMEGA ® + + K K Limited Use in Vacuum NICKEL- NICKEL- – – ALUMINUM or Reducing. Wide –270 to 1372°C –6.458 to – – CHROMIUM Temperature Ni-AI Range, Most Popular –454 to 2501°F 54.886 Ni-Cr (magnetic) H Calibration
— assets.omega.com, retrieved 2026-08-19
What tc-inc.com says
Thermocouple Output Tolerances to IEC 60584-1 | Type | + Leg | - Leg | 100ºC | 500ºC | 1000ºC | Continuous | Short Term | Type | Class 1 | Class 2 | K | NICKEL - CHROMIUM Also known as: Chromel™, Thermokanthal KP*, NiCr, T1*, Tophel™ | NICKEL - Aluminum (magnetic) Also known as: Ni-Al, Alumel™, Thermokanthal KN™, T2™, NiAl™ | 42 | 43 | 39 | 0 to +1100ºC | -180 to +1350ºC | Temperature Range Tolerance Value Temperature Range Tolerance Value | –40°C to +375°C ±1.5°C 375°C to 1000°C ±0.004 ⋅ |t| | –40°C to +333°C ±2.5°C 333°C to 1200°C ±0.0075 ⋅ |t|
— tc-inc.com, retrieved 2026-08-19
What tc.co.uk says
What is the Colour Code for a Type K Thermocouple? In the UK and Europe, the most widely used colour code for Type K thermocouple cable is to the international IEC 60584-3 standard which is as follows: Positive Leg = Green, Negative Leg = White, Outer Sheath (Jacket) = Green, Thermocouple Connector Colour = Green
— tc.co.uk, retrieved 2026-08-19
Sources
- thermometricscorp.comhttps://thermometricscorp.com/thermocouple-color-codes.html
- assets.omega.comhttps://assets.omega.com/pdf/test-and-measurement-equipment/temperature/sensors/thermocouple-probes/tc_colorcodes.pdf
- tc-inc.comhttps://www.tc-inc.com/thermocouple/thermocouple-tolerances.html
- tc.co.ukhttps://www.tc.co.uk/thermocouple-information/thermocouple-colour-code.html