Thermal Conductivity Converter
Convert thermal conductivity between units instantly. Includes conversion tables, common equivalents, and calculation formulas.
Calculator
Adjust values & calculateAll Conversions
| Unit | Value |
|---|---|
| W/(m*K) | 1 |
| kW/(m*K) | 0.001 |
| W/(cm*K) | 0.01 |
| cal/(s*cm*C) | 0.00238846 |
| kcal/(h*m*C) | 0.859845 |
| BTU/(h*ft*F) | 0.577789 |
| BTU*in/(h*ft2*F) | 6.93347 |
Material Thermal Conductivity (W/(m*K))
| Material | W/(m*K) | BTU/(h*ft*F) |
|---|---|---|
| Copper | 401 | 231.693 |
| Aluminum | 237 | 136.936 |
| Iron | 80.2 | 46.339 |
| Stainless Steel | 16.3 | 9.418 |
| Glass | 1.05 | 0.607 |
| Water | 0.606 | 0.350 |
| Wood (oak) | 0.17 | 0.098 |
| Air | 0.026 | 0.015 |
| Fiberglass Insulation | 0.04 | 0.023 |
| Polyurethane Foam | 0.025 | 0.014 |
Formula
Thermal conductivity conversion uses W/(m*K) as the base unit. Key factors: 1 BTU/(h*ft*F) = 1.730735 W/(m*K), 1 cal/(s*cm*C) = 418.68 W/(m*K). The conversion combines energy, length, and temperature unit changes. R-value (insulation rating) is inversely proportional to thermal conductivity.
Last reviewed: December 2025
Worked Examples
Example 1: Building Insulation Specification
Example 2: Heat Sink Material Comparison
Background & Theory
The Thermal Conductivity Converter applies the following established principles and formulas. Unit conversion is the process of expressing a quantity in a different unit of measurement while preserving its physical meaning. At the foundation of modern measurement lies the International System of Units (SI), which defines seven base units: the meter for length, kilogram for mass, second for time, ampere for electric current, kelvin for thermodynamic temperature, mole for amount of substance, and candela for luminous intensity. All other units, called derived units, are defined as algebraic combinations of these seven. Dimensional analysis is the principal method for performing unit conversions. By treating units as algebraic quantities that can be multiplied, divided, and cancelled, a conversion factor chain allows a value expressed in one unit to be rewritten in another without altering its physical magnitude. For example, to convert 60 miles per hour to meters per second, one multiplies by a chain of conversion factors each equal to one: (1609.34 m / 1 mile) × (1 hour / 3600 s). Metric prefixes enable compact expression of quantities across extreme ranges of magnitude. Standard prefixes span from nano (10^-9) through micro (10^-6) and milli (10^-3) up through kilo (10^3), mega (10^6), and giga (10^9), and beyond in both directions. These prefixes are strictly multiplicative and apply consistently to any SI base or derived unit. Temperature conversions require affine transformations rather than simple scaling. To convert Celsius to Fahrenheit the formula is °F = (°C × 9/5) + 32, while the conversion to the absolute Kelvin scale is K = °C + 273.15. These formulas reflect the different zero points and degree-size conventions of each scale. Significant figures govern how precision is preserved through calculations. A result should not express more precision than the least precise input value permits. In digital storage, IEEE and IEC standards distinguish between decimal prefixes (kilobyte = 1000 bytes) and binary prefixes (kibibyte = 1024 bytes), a distinction that has practical consequences for how storage capacity is reported by manufacturers versus operating systems. Unit coherence — ensuring that all quantities in an equation share a consistent unit system — is essential for obtaining correct results.
History
The history behind the Thermal Conductivity Converter traces back through the following developments. Human beings have been measuring and comparing quantities since before recorded history. The earliest known measurement units were body-based: the cubit (the distance from elbow to fingertip), the foot, the hand, and the digit. The furlong originated as the length of a furrow a team of oxen could plow without resting. These anthropomorphic standards were practical for local use but differed between regions and kingdoms, creating persistent difficulties in trade and construction. The ancient Egyptians standardized the royal cubit at approximately 52.4 centimeters and distributed calibrated granite rods to ensure consistency across building projects, including the pyramids. Roman engineers used the mile (mille passuum, one thousand double paces) and spread these standards throughout their empire via road networks. Despite these efforts, measurement diversity persisted across medieval Europe, hampering commerce. The French Revolution created political will for radical standardization. In 1795 France officially adopted the metric system, defining the meter as one ten-millionth of the distance from the equator to the North Pole along the Paris meridian. This gave the world its first fully decimal, rationally constructed measurement system. The Metre Convention of 1875 established the International Bureau of Weights and Measures (BIPM) in Sevres, France, creating a permanent international body to maintain physical artifact standards and coordinate global metrology. For over a century, the kilogram was defined by a platinum-iridium cylinder locked in a vault near Paris. In 1999, a stark demonstration of what unit inconsistency costs occurred when NASA's Mars Climate Orbiter was lost because one engineering team used pound-force seconds while another used newton seconds. The spacecraft entered the Martian atmosphere at the wrong angle and was destroyed, at a cost of 327 million dollars. In 2019 the SI underwent its most significant revision, redefining all seven base units in terms of fixed numerical values of fundamental physical constants such as the speed of light, Planck's constant, and the elementary charge. This eliminated any reliance on physical artifacts and made the measurement system permanently stable and universally reproducible.
Frequently Asked Questions
Formula
Converted Value = Input Value x (From Factor / To Factor)
Thermal conductivity conversion uses W/(m*K) as the base unit. Key factors: 1 BTU/(h*ft*F) = 1.730735 W/(m*K), 1 cal/(s*cm*C) = 418.68 W/(m*K). The conversion combines energy, length, and temperature unit changes. R-value (insulation rating) is inversely proportional to thermal conductivity.
Worked Examples
Example 1: Building Insulation Specification
Problem: Fiberglass insulation has k = 0.04 W/(m*K). Convert to BTU*in/(h*ft2*F) and calculate R-value per inch.
Solution: To BTU*in/(h*ft2*F): 0.04 / 0.1442279 = 0.2773\nR-value per inch = 1 / (conductance per inch)\nR per inch = 0.0254 m / (0.04 W/(m*K)) = 0.635 m2*K/W\nConvert to imperial: 0.635 / 0.17611 = 3.60 ft2*F*h/BTU per inch
Result: k = 0.04 W/(m*K) = 0.277 BTU*in/(h*ft2*F), R-3.6 per inch
Example 2: Heat Sink Material Comparison
Problem: Compare copper (401 W/(m*K)) and aluminum (237 W/(m*K)) in BTU/(h*ft*F).
Solution: Copper: 401 / 1.730735 = 231.7 BTU/(h*ft*F)\nAluminum: 237 / 1.730735 = 136.9 BTU/(h*ft*F)\nRatio: 401/237 = 1.69, so copper conducts heat 69% better
Result: Copper: 231.7, Aluminum: 136.9 BTU/(h*ft*F)
Frequently Asked Questions
What is thermal conductivity?
Thermal conductivity (k or lambda) measures how well a material conducts heat. It is defined as the rate of heat transfer through a unit thickness of material per unit area per unit temperature difference. The SI unit is W/(m*K). High values (like copper at 401 W/(m*K)) mean the material conducts heat efficiently, while low values (like air at 0.026 W/(m*K)) indicate good insulation properties.
What is the relationship between thermal conductivity and R-value?
R-value (thermal resistance) is the inverse of thermal conductance. For a material of thickness L and thermal conductivity k, the R-value equals L/k. Lower thermal conductivity means higher R-value (better insulation). In US customary units, R-value is in ft2*F*h/BTU. Fiberglass insulation has low k (0.04 W/(m*K)) giving high R-value, while metals have high k giving negligible R-value for the same thickness.
Why do metals have high thermal conductivity?
Metals have high thermal conductivity because their free electrons can rapidly transfer kinetic energy through the material. In metallic bonding, outer electrons are delocalized and move freely through the crystal lattice. These electrons carry thermal energy much faster than the lattice vibrations (phonons) that dominate heat transfer in non-metals. This is why copper and aluminum are preferred for heat sinks and cooking pans.
What inputs do I need to use Thermal Conductivity Converter accurately?
Each field is labelled with the required unit (metric or imperial). Gather your source values before starting — for example, a weight measurement in kilograms, a distance in metres, or a dollar amount — and enter them exactly as measured. The formula section on this page lists every variable and explains what each represents.
How do I verify Thermal Conductivity Converter's result independently?
The Formula section on this page shows the equation used. You can reproduce the calculation manually or in a spreadsheet using those steps. Compare your answer against the worked examples in the Examples section, which use known reference values so you can confirm the calculator is behaving as expected.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy