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Thermal Conductivity Converter

Science

Convert thermal conductivity between W/m·K, BTU/(hr·ft·°F), cal/(s·cm·°C), and BTU·in/(hr·ft²·°F) — used for materials science and insulation design.

Reviewed by the thecalcu.com team · Last updated July 30, 2026

From
To
All conversionsfor 1 Watts per Metre-Kelvin (W/m·K)
Watts per Metre-Kelvin (W/m·K)1
BTU per Hour-Foot-°F (BTU/(hr·ft·°F))0.57779087
Calories per Second-Centimetre-°C (cal/(s·cm·°C))0.0023900574
BTU·in per Hour-Foot²-°F (BTU·in/(hr·ft²·°F))6.9334665

What is a Thermal Conductivity?

The Thermal Conductivity Converter converts thermal conductivity between watts per metre-Kelvin (the SI unit), BTU per hour-foot-°F (the standard imperial unit), calories per second-centimetre-°C (a CGS unit still used in some scientific literature), and BTU·inch per hour-foot²-°F (the common US insulation "k-value" unit). Thermal conductivity is an intrinsic material property describing how readily heat passes through a substance.

Enter a value in any supported unit and the converter calculates the equivalent instantly. For the related quantity that accounts for specific component geometry, see the Thermal Resistance Converter.

Why Use a Thermal Conductivity Converter?

Materials datasheets from different countries and industries report thermal conductivity in different unit conventions, SI-based W/m·K from international suppliers, imperial BTU/(hr·ft·°F) from US engineering references, and specialised insulation "k-value" units from building materials manufacturers. Comparing materials across these sources for a design decision requires accurate conversion between them.

Who Should Use This Converter?

  • Materials engineers comparing thermal conductivity specifications across international datasheets.
  • Building and insulation engineers converting between SI thermal conductivity and the US insulation industry's BTU·in/(hr·ft²·°F) convention.
  • Mechanical engineers performing heat transfer calculations that combine data sources using different unit systems.
  • Physics and materials science students working with CGS-based conductivity data from older references.

What Insights Does the Thermal Conductivity Converter Give You?

The main output is the converted value in your chosen target unit, calculated precisely from the fixed multiplier relationship between units. Because thermal conductivity spans several orders of magnitude across common materials (from excellent conductors like copper to excellent insulators like foam), the converter helps you sanity-check whether a value falls in the expected range for the type of material involved.

How to use this Thermal Conductivity calculator

  1. Choose your starting unit from the source dropdown, for example, "Watts per Metre-Kelvin (W/m·K)".
  2. Enter the numeric value you want to convert in the input field.
  3. Choose your target unit from the destination dropdown, for example, "BTU per Hour-Foot-°F".
  4. Read the converted result, which updates instantly as you type or change units.
  5. Use the swap (⇅) button if you need to reverse the conversion direction.
  6. Use the copy button to grab the result for a materials comparison or heat transfer calculation.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The converter's base unit is watts per metre-Kelvin (W/m·K). Every supported unit has a fixed multiplier:

- 1 BTU/(hr·ft·°F) ≈ 1.73073 W/m·K
- 1 cal/(s·cm·°C) = 418.4 W/m·K
- 1 BTU·in/(hr·ft²·°F) ≈ 0.144228 W/m·K

Any conversion follows:

Result = Input × (toBase of source unit ÷ toBase of target unit)

Worked example, converting copper's thermal conductivity of 400 W/m·K to BTU/(hr·ft·°F):

Result = 400 × (1 ÷ 1.73073) = 231.15 BTU/(hr·ft·°F)

This matches the commonly cited imperial-unit value for copper's excellent thermal conductivity.

Related Tools

You may also find these useful: Specific Heat Capacity Converter.

Frequently Asked Questions

What is thermal conductivity?
Thermal conductivity measures how well a material conducts heat, expressed as the rate of heat flow through a unit thickness of material per unit temperature difference. Materials with high thermal conductivity (like copper) transfer heat readily, while materials with low thermal conductivity (like foam insulation) resist heat flow.
How do I convert W/m·K to BTU/(hr·ft·°F)?
Divide the W/m·K value by 1.73073, since one BTU/(hr·ft·°F) equals approximately 1.73073 W/m·K. Enter your value with 'Watts per Metre-Kelvin (W/m·K)' as the source and 'BTU per Hour-Foot-°F' as the target to apply this automatically.
Why do insulation materials use BTU·in/(hr·ft²·°F) instead of the standard thermal conductivity unit?
This unit (sometimes written as 'k-value' in insulation contexts) is scaled specifically for typical insulation thickness (inches) and area (square feet), producing more intuitively-sized numbers for the thin, low-conductivity materials used in building insulation, compared to the standard per-length-per-area conductivity unit.
What is a typical thermal conductivity value for common materials?
Copper has a thermal conductivity of about 400 W/m·K (excellent conductor), while common building insulation materials range from about 0.02 to 0.04 W/m·K (excellent insulator), a difference of roughly four orders of magnitude between the best conductors and best insulators.
How does thermal conductivity relate to thermal resistance?
Thermal conductivity is an intrinsic material property, while thermal resistance depends on both the material's conductivity and its specific geometry (thickness and area), you calculate a component's thermal resistance from its material's thermal conductivity once you know its dimensions. See the [Thermal Resistance Converter](/thermal-resistance-converter/) for that related quantity.
Why do CGS units like cal/(s·cm·°C) still appear in some references?
Older scientific literature and some materials science references still use CGS-based thermal conductivity units, particularly in contexts with strong historical ties to the CGS system, this converter includes that unit for compatibility with such sources.
How does thermal conductivity affect insulation R-value?
R-value (thermal resistance per unit area) is inversely related to thermal conductivity for a given material thickness, lower thermal conductivity produces a higher R-value for the same thickness, which is why insulation materials are specifically engineered to have very low thermal conductivity.
Does thermal conductivity change with temperature?
Yes, most materials' thermal conductivity varies somewhat with temperature, which is why precise engineering references specify thermal conductivity at a stated reference temperature rather than treating it as a single fixed constant across all conditions.
Who typically needs to convert thermal conductivity units?
Materials engineers comparing datasheets from different international suppliers, building engineers working with insulation specifications across metric and imperial systems, and mechanical engineers doing heat transfer calculations that mix data sources all commonly need to convert between thermal conductivity units.
How does thermal conductivity feed into a heat transfer coefficient calculation?
Thermal conductivity, combined with a material's thickness, gives a conductive heat transfer coefficient for that specific layer, see the [Heat Transfer Coefficient Converter](/heat-transfer-coefficient-converter/) for unit conversions of the resulting per-area heat transfer rate.
Also known as
thermal conductivity converterw/mk to btu/hr ft f converterk value converter insulationthermal conductivity unitscal/s cm c converter