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Thermal Conductivity Converter

Convert between thermal conductivity units: W/(m·K), BTU/(hr·ft·°F), and cal/(s·cm·°C)

Input Value

Input Unit

W/(m·K)

1.000000

Watts per meter-Kelvin (SI unit)

BTU/(hr·ft·°F)

0.577789

BTU per hour-foot-Fahrenheit (Imperial)

cal/(s·cm·°C)

0.00239006

Calories per second-centimeter-Celsius (CGS)

Common Material Thermal Conductivity

Material	Category	W/(m·K)	BTU/(hr·ft·°F)	cal/(s·cm·°C)
Silver	Metal	429	247.9	1.025
Copper	Metal	401	231.7	0.958
Aluminum	Metal	237	136.9	0.566
Steel	Metal	50	28.9	0.119
Concrete	Building	1.4	0.81	0.00335
Brick	Building	0.72	0.42	0.00172
Wood (pine)	Building	0.12	0.069	0.000287
Fiberglass insulation	Insulation	0.04	0.023	0.0000956
Polyurethane foam	Insulation	0.026	0.015	0.0000621
Air (still)	Gas	0.024	0.014	0.0000574

Understanding Thermal Conductivity

Thermal Conductivity (k-value) is a material property that measures how well a material conducts heat. Higher values mean heat passes through more easily, while lower values indicate better insulation properties.

Unit Definitions

W/(m·K): SI unit - Watts per meter-Kelvin. Standard for international use.
BTU/(hr·ft·°F): Imperial unit - British Thermal Units per hour-foot-Fahrenheit. Common in US construction.
cal/(s·cm·°C): CGS unit - Calories per second-centimeter-Celsius. Used in some scientific contexts.

Material Selection Guide

High conductivity (k > 50): Metals - Used for heat sinks, cookware, heat exchangers
Medium conductivity (1 < k < 50): Stone, concrete - Structural materials with moderate thermal mass
Low conductivity (k < 1): Wood, brick - Building materials with some insulation value
Very low conductivity (k < 0.1): Insulation materials - Foam, fiberglass, air gaps

HVAC Applications

Selecting insulation materials for walls, roofs, and pipes
Designing heat exchangers and HVAC ductwork
Calculating thermal bridging in building envelopes
Analyzing heat loss through building components
Comparing material performance for energy efficiency

Relationship to R-Value

Thermal conductivity (k) is inversely related to R-value: R = thickness / k. Materials with low thermal conductivity produce high R-values when used as insulation.

Frequently Asked Questions

What is thermal conductivity?

Thermal conductivity (k-value) is a material property that quantifies how easily heat flows through a material. It's measured as heat flow rate per unit area per unit temperature gradient.

Is high or low thermal conductivity better for insulation?

LOW thermal conductivity is better for insulation. Materials with k < 0.1 W/(m·K) are considered good insulators. Metals have high k-values (100-400 W/(m·K)) and are poor insulators but excellent conductors.

How does thermal conductivity relate to R-value?

R-value = thickness / thermal conductivity. For example, 1 inch (0.0254 m) of material with k = 0.04 W/(m·K) has R-value = 0.0254/0.04 = 0.635 m²·K/W (or R-3.6 in imperial units).

Which unit should I use?

Use W/(m·K) for international/scientific work and SI-based energy modeling. Use BTU/(hr·ft·°F) for US construction and HVAC specifications. The cal/(s·cm·°C) unit is rarely used except in older scientific literature.

Does thermal conductivity change with temperature?

Yes, thermal conductivity varies with temperature for most materials. Values are typically given at room temperature (20-25°C). For precise calculations at extreme temperatures, use temperature-adjusted values.

What makes a good thermal conductor vs. insulator?

Good conductors (metals) have free electrons that transfer heat efficiently. Good insulators (foam, fiberglass) trap air and minimize molecular movement. Air has very low conductivity (0.024 W/(m·K)), making trapped air an excellent insulator.

Related Converters

R-Value to U-Value

Thermal resistance conversion

U-Value to R-Value

Thermal transmittance conversion

Specific Heat

Heat capacity conversions

BTU/hr to Watts

Thermal power conversion

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