Sources and scope for this page: Compiled engineering handbook values (physical property data, no governing revision), covering thermal conductivity values for all materials listed. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. Full sources, values and limits on this page.
Page last changed 2026-11-08 · based on n/a — physical property data, no governing revision
Quick Answer
Thermal Conductivity of Common Materials
| Material[2] | Conductivity W/m·K[2] | Conductivity BTU·in/h·ft²·°F[1] | Class[2] |
|---|---|---|---|
| Silver # | 429 | 2971 | Metal |
| Copper # | 401 | 2777 | Metal |
| Gold # | 317 | 2196 | Metal |
| Aluminium # | 237 | 1642 | Metal |
| Brass (70/30) # | 110 | 762 | Metal |
| Nickel # | 90 | 623 | Metal |
| Iron, pure # | 80 | 554 | Metal |
| Steel, carbon 1% # | 43 | 298 | Metal |
| Lead # | 35 | 242 | Metal |
| Titanium # | 22 | 152 | Metal |
| Stainless 316 # | 16.3 | 113 | Metal |
| Stainless 304 # | 16.2 | 112 | Metal |
| Inconel 718 # | 11.4 | 79 | Metal |
| Glass, window # | 1.05 | 7.3 | Non-metal |
| Concrete # | 1.7 | 11.8 | Non-metal |
| Brick, common # | 0.6 | 4.2 | Non-metal |
| Water (20 °C) # | 0.6 | 4.2 | Fluid |
| Engine oil # | 0.145 | 1.0 | Fluid |
| PVC # | 0.19 | 1.3 | Polymer |
| PTFE # | 0.25 | 1.7 | Polymer |
| PEEK # | 0.25 | 1.7 | Polymer |
| Delrin (POM) # | 0.31 | 2.1 | Polymer |
| Wood, oak # | 0.17 | 1.2 | Non-metal |
| Air (20 °C) # | 0.026 | 0.18 | Gas |
Values are at approximately 20–25 °C. Thermal conductivity is temperature-dependent, and for alloys it also depends on composition and heat treatment — a specific grade's value should come from its own data sheet where precision matters.
The Unit and Why It Matters
Thermal conductivity k is the heat flow through a unit thickness for a unit temperature difference: W/m·K in metric, BTU·in/h·ft²·°F in imperial. The imperial unit contains inches rather than feet because conduction calculations usually involve a wall or sheet of known thickness in inches.
The two are not a simple ratio because of the inch in the imperial unit — the conversion factor is 6.933, not 5.678 (which is the factor for BTU·ft/h·ft²·°F).
What the Range Tells You
The spread is enormous — four orders of magnitude from silver to air.
- Pure metals conduct best, and the best conductors are also the best electrical conductors. This is not a coincidence: in metals, free electrons carry both heat and charge.
- Alloying sharply reduces conductivity. Pure copper is 401; adding zinc to make brass drops it to about 110, and adding chromium and nickel to make stainless drops it to 16. The alloying elements scatter the electrons that were doing the conducting.
- Polymers and gases are insulators, which is why foams work: the polymer structure is weak enough, but the trapped gas is what actually stops the heat.
A practical consequence for machining: stainless steel, titanium and nickel alloys conduct heat away from the cutting edge poorly, so the heat stays in the tool. That is a large part of why they are difficult to machine.
Frequently Asked Questions
- What is the thermal conductivity of copper?
- About 401 W/m·K at room temperature — the highest of the common engineering metals after silver. This is why copper is used for heatsinks, heat exchangers and bus bars.
- What is the thermal conductivity of stainless steel?
- About 16 W/m·K for 304 and 316 at room temperature — roughly 25 times lower than copper, and about a quarter of that of plain carbon steel. This low conductivity is what makes stainless useful as an insulator in cryogenic equipment, and difficult to weld and machine.
- What is the thermal conductivity of aluminium?
- About 237 W/m·K for pure aluminium. Alloying reduces it — 6061 is about 167 and 7075 about 130 — but it remains far better than steel, which is why aluminium heatsinks are common even though copper performs better per unit volume.
- Which metal conducts heat best?
- Silver, at about 429 W/m·K, followed by copper at 401 and gold at 317. Silver is rarely used because of cost; copper gives most of the performance at a fraction of the price.
- Does thermal conductivity change with temperature?
- Yes. For metals it generally falls as temperature rises, because lattice vibrations scatter the conducting electrons more. For gases it rises with temperature. The values here are at room temperature.
- What is the difference between thermal conductivity and thermal conductance?
- Conductivity (k) is a property of the material alone. Conductance (U or h) also includes the thickness and area of a specific part — it is conductivity divided by thickness. A thin sheet of a poor conductor can have higher conductance than a thick slab of a better one.
Related
Value Sources
References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.
| # | Source | Type | Revision / method |
|---|---|---|---|
| [1] | Imperial conversion | derived | W/m·K × 6.933 = BTU·in/h·ft²·°F (the inch-based form of the imperial unit). |
| [2] | Standard engineering handbook values (ASM Metals Reference Book and comparable sources) | reference | n/a — compiled physical property data, not a revisioned specification — source |
Data Sources
| Standard | Revision | What it covers on this page |
|---|---|---|
| Compiled engineering handbook values | n/a — physical property data, no governing revision | thermal conductivity values for all materials listed |
Verification scope
No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.
Derived values — the following values on this page are calculated, not taken directly from the standard:
| Value | How it is derived |
|---|---|
| Imperial conductivity column | W/m·K × 6.933. |
Values are typical room-temperature figures. Conductivity varies with temperature, and for alloys with composition and condition — use the specific grade data sheet where precision matters.
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