Thermal Conductivity Converter

Thermal conductivity measures how readily a material conducts heat through its bulk — how much heat energy passes through a unit thickness of the material, across a unit area, for each degree of temperature difference. It's a fundamental material property that determines whether something feels like a good insulator (low conductivity, like foam or wool) or a good conductor (high conductivity, like copper or aluminum).

Our Thermal Conductivity converter supports the SI unit, watt/meter/K (W/(m·K)), along with watt/centimeter/°C and kilowatt/meter/K for different scales of measurement. Calorie-based units — calorie (IT and th)/second/centimeter/°C and kilocalorie (IT and th)/hour/meter/°C — appear in older thermodynamic references and some European engineering traditions. For US engineering and building science, the converter includes Btu-inch and Btu-foot conductivity units per second or per hour, per square foot, per degree Fahrenheit — the units that appear on US insulation and building material datasheets.

To use the converter, select your starting and target units from the dropdown lists and enter a value — the result is calculated instantly to up to 12 significant digits. For example, converting 1 W/(m·K) to Btu(IT)·inch/(hour·square foot·°F) gives about 6.933 — a conversion needed constantly when comparing a European material's conductivity spec (in W/(m·K)) to a US insulation R-value calculation (built from Btu-inch units).

Thermal conductivity values span an enormous range: good insulators like fiberglass, foam, and still air sit around 0.02-0.04 W/(m·K), wood and common building materials fall in the 0.1-0.2 W/(m·K) range, glass is around 1 W/(m·K), and metals are dramatically higher — aluminum around 205 W/(m·K) and copper around 400 W/(m·K), roughly 10,000 times more conductive than typical insulation. This wide range is exactly why insulation materials work: their low conductivity slows heat flow to a crawl compared to the metals and structural materials they protect.

Thermal conductivity conversions matter in building envelope design (insulation R-values and U-values are built from underlying conductivity values), materials science and product engineering (selecting materials for heat sinks versus thermal barriers), and HVAC and process engineering (heat exchanger and pipe insulation design). Because building codes, material datasheets, and engineering standards from different countries default to different unit systems, having one reliable converter avoids costly specification errors when comparing or combining data from multiple sources.

All conversion factors used in this tool are drawn from standard, internationally recognized unit definitions, so results are dependable for building science, materials engineering, and technical documentation. The converter is free, requires no account, and works equally well on desktop and mobile devices.

Thermal conductivity is also the starting point for calculating thermal resistance — divide a material's thickness by its conductivity (times area) to get its resistance to heat flow — so a precise conductivity value from this converter feeds directly into the Thermal Resistance converter elsewhere in this section for full insulation and heat-loss calculations.