What is thermal conductivity?

Thermal conductivity (k) is a material property that describes how readily heat flows through it. A high k (e.g., copper at ~400 W/m·K) means the material conducts heat easily; a low k (e.g., aerogel at ~0.015 W/m·K) means it is a good insulator.

What is Fourier's law?

Fourier's law states that the heat flux through a material is q = k × (ΔT / L), where ΔT is the temperature difference across the slab and L is its thickness. Total heat flow is Q = q × A, where A is the cross-sectional area.

Are these values exact?

No. They are indicative room-temperature values. Conductivity varies with temperature, density, moisture, purity, composition, and manufacturing process. For design or compliance work, use product-specific measured data. ASTM C177 covers guarded-hot-plate measurements for flat homogeneous specimens; ASTM C518 is a comparative heat-flow-meter method.

Why are metals much more conductive than polymers?

Heat conduction in metals is dominated by free electrons, which transfer energy very efficiently. Polymers and ceramics rely on slower phonon (lattice vibration) conduction, resulting in conductivity values one to four orders of magnitude lower than metals.

Can I use this for composite or laminated walls?

This calculator handles a single homogeneous layer. For multilayer walls, calculate each layer's thermal resistance R = L/(k×A) separately and sum them: Q = ΔT_total / R_total.

Thermal Conductivity Material Reference

Compare indicative room-temperature conductivity values and calculate steady-state heat flow, RSI/R-value, and U-value for one homogeneous slab.

Material Thermal Conductivity Reference

Table unit

	Category		Use

Indicative values near room temperature—not product specifications. Click Use to load the SI k value.

Fourier Heat-Flow Calculator

Steady-state conduction through a flat slab: q = k · (ΔT / L)

Thermal Conductivity k (W/m·K)

W/m·K

Wall / Slab Thickness L

Cross-sectional Area A

Hot-side Temp T₁

Cold-side Temp T₂

°C

Scope, data quality, and sources

This is a screening reference for one flat, homogeneous layer at steady state. Listed k values are indicative: temperature, density, moisture, purity, grain structure, and product formulation can materially change them. The calculated U-value excludes surface films, framing, thermal bridges, contact resistance, radiation, convection, and air leakage, so it is not an assembly compliance value.

Primary references: NIST compilation of solid materials, NIST SRD 81 building and insulation database, 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.

Summary

This tool provides thermal conductivity (k) values in W/m·K for over 40 common engineering materials including metals, alloys, polymers, ceramics, insulation, and building materials. Values are typical at or near room temperature (~25 °C). The built-in Fourier's law calculator lets you compute steady-state conductive heat flux (W/m²) and total heat flow (W) through a flat slab given its thickness, area, and surface temperatures.

How it works

Type a material name in the search box to filter the reference table instantly.
Click any row to pre-fill the material's k value into the Fourier's law calculator.
Enter wall thickness, area, and the hot- and cold-side temperatures in the calculator.
Click Calculate to see heat flux (W/m²) and total heat flow (W) for the slab.
Use the category filter buttons to browse metals, polymers, insulation, and more.

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.
Quick look-up during thermal analysis or FEA preprocessing.
Teaching or studying heat transfer fundamentals.
Cross-checking material data in engineering datasheets.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu