Thermal Conductivity Material Reference
Compare room-temperature conductivity values for 77 materials, convert them to R per inch, and calculate heat flow through a single slab or the U-value of a multilayer wall.
Thermal conductivity k, in W/m·K, is the heat in watts that flows through a 1 m thick layer per square meter of area for each kelvin of temperature difference.
Use the Thermal Conductivity Material Reference
Thermal Conductivity of Materials (77)
| R per inch | Use | ||
|---|---|---|---|
| ABS plastic | 0.170 | R-0.85 | |
| Acrylic (PMMA) | 0.190 | R-0.76 | |
| Aerogel blanket | 0.015 | R-9.6 | |
| Air (still, 25 °C) | 0.026 | R-5.5 | |
| Alumina (Al₂O₃, 99.5%) | 30 | — | |
| Aluminum (pure) | 237 | — | |
| Aluminum alloy 2024-T6 | 177 | — | |
| Aluminum alloy 6061-T6 | 167 | — | |
| Aluminum bronze (90Cu-10Al) | 52 | — | |
| Aluminum nitride (AlN) | 180 | — | |
| Beryllium copper C17200 (aged) | 105 | — | |
| Borosilicate glass | 1.14 | R-0.13 | |
| Carbon steel (1% C) | 43 | — | |
| Carbon steel AISI 1010 | 63.9 | — | |
| Cartridge brass (70Cu-30Zn) | 110 | — | |
| Cast iron (grey) | 48 | — | |
| Cellulose (loose fill) | 0.040 | R-3.6 | |
| Chromium | 93.7 | — | |
| Concrete (stone mix) | 1.4 | R-0.10 | |
| Constantan (55Cu-45Ni) | 23 | — | |
| Copper (pure) | 401 | — | |
| Cork board | 0.039 | R-3.7 | |
| Diamond (type IIa) | 2300 | — | |
| Epoxy resin | 0.350 | R-0.41 | |
| Expanded polystyrene (EPS) | 0.036 | R-4.0 | |
| Extruded polystyrene (XPS) | 0.029 | R-5.0 | |
| Fused silica glass | 1.38 | R-0.10 | |
| Glass wool (fiberglass) | 0.044 | R-3.3 | |
| Gold | 317 | — | |
| Granite | 2.79 | R-0.05 | |
| Gypsum board (drywall) | 0.170 | R-0.85 | |
| Hardwood (oak, maple) | 0.160 | R-0.90 | |
| Hollow concrete block | 0.510 | R-0.28 | |
| Ice (0 °C) | 2.18 | R-0.07 | |
| Inconel 625 | 9.8 | — | |
| Iron (pure) | 80.2 | — | |
| Lead | 35.3 | — | |
| Limestone | 2.15 | R-0.07 | |
| Magnesium | 156 | — | |
| Marble | 2.8 | R-0.05 | |
| Mineral wool (rock wool) | 0.040 | R-3.6 | |
| Molybdenum | 138 | — | |
| Natural rubber (soft) | 0.130 | R-1.11 | |
| Nichrome (80Ni-20Cr) | 12 | — | |
| Nickel | 90.7 | — | |
| Nylon 6,6 (PA66) | 0.250 | R-0.58 | |
| PEEK | 0.250 | R-0.58 | |
| Phosphor bronze (89Cu-11Sn) | 54 | — | |
| Plain carbon steel | 60.5 | — | |
| Plate glass (soda-lime) | 1.4 | R-0.10 | |
| Platinum | 71.6 | — | |
| Plywood | 0.120 | R-1.20 | |
| Polycarbonate (PC) | 0.200 | R-0.72 | |
| Polyethylene (HDPE) | 0.460 | R-0.31 | |
| Polypropylene (PP) | 0.220 | R-0.66 | |
| Polyurethane foam (rigid) | 0.026 | R-5.5 | |
| PTFE (Teflon) | 0.250 | R-0.58 | |
| PVC (rigid) | 0.190 | R-0.76 | |
| Sand (dry) | 0.270 | R-0.53 | |
| Sandstone | 2.9 | R-0.05 | |
| Sapphire (Al₂O₃ single crystal) | 46 | — | |
| Silicon (Si) | 148 | — | |
| Silicon carbide (sintered) | 120 | — | |
| Silicone rubber | 0.250 | R-0.58 | |
| Silver | 429 | — | |
| Softwood (pine, fir) | 0.120 | R-1.20 | |
| Soil (dry) | 0.520 | R-0.28 | |
| Solid brick (common) | 0.720 | R-0.20 | |
| Stainless steel 304 | 14.9 | — | |
| Stainless steel 316 | 13.4 | — | |
| Tin | 66.6 | — | |
| Titanium | 21.9 | — | |
| Titanium Ti-6Al-4V | 6.7 | — | |
| Tungsten | 174 | — | |
| Vacuum insulated panel | 0.008 | R-18.0 | |
| Water (liquid, 25 °C) | 0.607 | R-0.24 | |
| Zinc | 116 | — |
No materials match your search.
Fourier Heat-Flow Calculator
Steady-state conduction through a flat slab: q = k · (ΔT / L)
Q = k · A · ΔT / L
Multilayer Wall R-Value and U-Value
Layers in series: Rtotal = Rsi + Σ L/k + Rse, U = 1 / Rtotal. Pick a material or type your own k.
| Layer | R (m²·K/W) | Share of R | Temp. drop |
|---|
Surface resistances follow ISO 6946 conventions. One-dimensional result: studs, fasteners, mortar joints and air leakage are not included, so a framed wall performs worse than this clear-field value.
Scope, data quality, and sources
This is a screening reference for flat layers at steady state. Listed k values are indicative: temperature, density, moisture, purity, grain structure, and product formulation can materially change them (stainless steel 304 goes from about 15 W/m·K at room temperature to about 20 W/m·K near 330 °C, while pure copper falls slightly as it heats). The calculated U-values exclude framing, thermal bridges, contact resistance, radiation inside cavities and air leakage, so they are not assembly compliance values.
Primary references: 300 K property tables in Incropera, DeWitt, Bergman & Lavine, Fundamentals of Heat and Mass Transfer (Appendix A); NIST compilation of solid materials; NIST SRD 81 building and insulation database; ISO 6946 (surface resistances); and ASTM C177 method scope. Verify critical inputs against the exact material grade and test temperature.
Privacy: calculations and filtering run locally in your browser; entries are not uploaded by this tool.
Quick answer
Thermal conductivity k, in W/m·K, is the heat in watts that flows through a 1 m thick layer per square meter of area for each kelvin of temperature difference. Metals sit in the tens to hundreds, stainless steel near 15, stone and concrete around 1 to 3, and insulation near 0.03 to 0.05 W/m·K.
Examples
| Material (about 300 K / 27 °C) | k (W/m·K) |
|---|---|
| Copper (pure) | 401 |
| Aluminum (pure) | 237 |
| Iron (pure) | 80.2 |
| Stainless steel 304 | 14.9 |
| Concrete (stone mix) | 1.4 |
| Mineral wool (rock wool) | 0.040 |
Search or sort the table, then click Use to calculate heat flow, R-value and U-value for your own slab or wall.
Summary
This tool lists thermal conductivity (k) values in W/m·K for 77 common engineering materials: pure metals, aluminum and copper alloys, steels, polymers, ceramics, stone, glass, insulation, building materials and fluids. Metal and most nonmetal values are the 300 K (about 27 °C) figures from standard heat-transfer property tables. The table converts to BTU/hr·ft·°F, the BTU·in/hr·ft²·°F "k-value" used for US insulation, and R-value per inch. A Fourier's law calculator gives heat flux, heat flow, RSI, R-value and U-value for one slab, and a layer calculator sums the R-values of a multilayer wall with ISO 6946 surface resistances.
How it works
- Type a material name in the search box or use the category buttons to filter the table.
- Switch the table unit between W/m·K, BTU/hr·ft·°F and BTU·in/hr·ft²·°F, or sort by name or k.
- Click Use on any row to load its k value into the single-slab Fourier calculator.
- Enter thickness, area and hot- and cold-side temperatures to get heat flux, heat flow, RSI/R-value and U-value.
- For a wall, roof or floor, add one row per layer in the multilayer calculator and choose the surface resistances to get total R and U.
Use cases
- Selecting insulation materials for walls, roofs, or pipes.
- Comparing metals for heat sink or heat exchanger design.
- Estimating heat loss through a building element or furnace wall.
- Checking the R-value and U-value of a stud-bay or masonry wall build-up.
- Quick look-up during thermal analysis or FEA preprocessing.
- Teaching or studying heat transfer fundamentals.