What is thermal conductivity?

Thermal conductivity is a property that measures how well a material conducts heat. It's defined by Fourier's law and describes the rate of heat flow through a material per unit area, per unit temperature gradient.

How do I convert W/(m.K) to BTU/(h.ft.F)?

Divide the W/(m.K) value by about 1.7307. For example, 401 W/(m.K) (copper) equals about 231.7 BTU/(h.ft.F).

What is R-value and how does it relate to thermal conductivity?

R-value measures thermal resistance, how well a material resists heat flow. It equals the material's thickness divided by its thermal conductivity: R = L / k. A higher R-value means better insulation.

What is the thermal conductivity of common materials?

Copper is about 401 W/(m.K), aluminum about 237 W/(m.K), glass about 1 W/(m.K), wood about 0.1 to 0.2 W/(m.K), fiberglass insulation about 0.04 W/(m.K), and still air about 0.026 W/(m.K).

How do I calculate R-value from thermal conductivity and thickness?

Divide the material's thickness by its thermal conductivity: R = L / k. Make sure the units are consistent, or let the calculator handle the conversion automatically.

What is the difference between thermal conductivity and thermal conductance?

Thermal conductivity (k) is a property of the material itself, independent of thickness. Thermal conductance (often called U-value) also accounts for the thickness of a specific piece of material, and equals conductivity divided by thickness.

What is a BTU-in/(h.ft2.F) unit used for?

It's the standard US unit for insulation product ratings, combining thermal conductivity with a one-inch thickness reference, which is why insulation is often rated per inch of material.

Why do metals have high thermal conductivity?

Metals conduct heat well because free electrons that carry electric current also transfer thermal energy efficiently between atoms, which is why good electrical conductors are usually also good heat conductors.

Is this thermal conductivity converter free to use?

Yes, it is completely free, requires no registration, and runs entirely in your browser with no usage limits.

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Thermal Conductivity Conversions

9 units · R-value calculator

Thermal Conductivity Converter

Convert instantly between W/(m·K), BTU/(h·ft·°F), BTU·in/(h·ft²·°F) and more, then calculate a material's R-value from its thermal conductivity and thickness.

9Conductivity units

401W/(m·K) for copper

0msServer round-trips

From

W/(m·K)

To

BTU/(h·ft·°F)

0.5778176398BTU/(h·ft·°F)

BTU/(h·ft·°F) = W/(m·K) / 1.730734666

Thermal conductivity (k)

Conductivity unit

Thickness

Thickness unit

2.5 m²K/W

R = thickness / k

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Thermal conductivity concepts & formulas

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Quick conversion table

Common values for your selected units in the converter above, updated automatically.

W/(m·K)	BTU/(h·ft·°F)

Thermal conductivity unit reference

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Frequently asked questions

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