Heat Transfer Coefficient Converter
Convert between convective heat transfer coefficient units — watts per square meter-kelvin, Btu per hour per square foot-°F, and more.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
25 W/(m²·K) = 4.4027546 Btu/(h·ft²·°F)
1 Watt per Square Meter per Kelvin = 0.17611018 Btu (IT) per Hour per Square Foot per °F
1 Btu (IT) per Hour per Square Foot per °F = 5.6782633 Watts per Square Meter per Kelvin
25 W/(m²·K) in every supported unit
What is a Heat Transfer Coefficient Converter?
The heat transfer coefficient (often called the "film coefficient") measures how effectively a moving fluid — air, water, oil — carries heat to or from a surface it's touching. A high coefficient means the fluid is an efficient heat carrier (fast-moving water, for instance), while a low coefficient means poor heat transfer (still air). It's the key figure engineers plug into convective heat-transfer calculations for everything from radiator design to building envelope heat loss.
Every unit here is defined relative to the SI watt-per-square-meter-per-kelvin unit by a fixed multiplier, letting a European heat-exchanger datasheet's kcal/(h·m²·°C), a US HVAC engineer's Btu/(h·ft²·°F), and a physics paper's W/(m²·K) all be compared directly.
Conversion chart: Watt per Square Meter per Kelvin to Btu (IT) per Hour per Square Foot per °F
Conversion table
| Watt per Square Meter per Kelvin (W/(m²·K)) | Btu (IT) per Hour per Square Foot per °F (Btu/(h·ft²·°F)) |
|---|---|
| 0.01 W/(m²·K) | 0.0017611018 Btu/(h·ft²·°F) |
| 0.1 W/(m²·K) | 0.017611018 Btu/(h·ft²·°F) |
| 1 W/(m²·K) | 0.17611018 Btu/(h·ft²·°F) |
| 2 W/(m²·K) | 0.35222037 Btu/(h·ft²·°F) |
| 3 W/(m²·K) | 0.52833055 Btu/(h·ft²·°F) |
| 5 W/(m²·K) | 0.88055092 Btu/(h·ft²·°F) |
| 10 W/(m²·K) | 1.7611018 Btu/(h·ft²·°F) |
| 20 W/(m²·K) | 3.5222037 Btu/(h·ft²·°F) |
| 50 W/(m²·K) | 8.8055092 Btu/(h·ft²·°F) |
| 100 W/(m²·K) | 17.611018 Btu/(h·ft²·°F) |
| 1000 W/(m²·K) | 176.11018 Btu/(h·ft²·°F) |
Supported Units
| Unit | Symbol | In W/(m²·K) |
|---|---|---|
| Watt per Square Meter per Kelvin | W/(m²·K) | 1 W/(m²·K) |
| Kilocalorie (IT) per Hour per Square Meter per °C | kcal/(h·m²·°C) | 1.163 W/(m²·K) |
| Calorie (IT) per Second per Square Centimeter per °C | cal/(s·cm²·°C) | 41868 W/(m²·K) |
| Btu (IT) per Hour per Square Foot per °F | Btu/(h·ft²·°F) | 5.6782633 W/(m²·K) |
| Btu (th) per Hour per Square Foot per °F | Btu(th)/(h·ft²·°F) | 5.6744659 W/(m²·K) |
| Btu (IT) per Second per Square Foot per °F | Btu/(s·ft²·°F) | 20441.748 W/(m²·K) |
| Kilocalorie (IT) per Hour per Square Foot per °C | kcal/(h·ft²·°C) | 12.518428 W/(m²·K) |
About These Parameters
- Value
- The heat transfer coefficient value you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The unit your input value is currently measured in — a physics reference's W/(m²·K), or a US HVAC design guide's Btu/(h·ft²·°F).
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly.
How Heat Transfer Coefficient Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to watts per square meter per kelvin. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Watt per Square Meter per Kelvin → Btu (IT) per Hour per Square Foot per °F: multiply by 0.17611018. For example, 25 W/(m²·K) × 0.17611018 = 4.4027546 Btu/(h·ft²·°F).
Newton's Law of Cooling
The heat transfer coefficient (h) is the proportionality constant in Newton's law of cooling: heat flux = h × (surface temperature − fluid temperature). A larger h means heat moves faster for the same temperature difference — still air might have h around 5-25 W/(m²·K), while forced water flow can reach several thousand, which is exactly why liquid cooling systems outperform air cooling by such a wide margin in high-power electronics and industrial equipment.
Convection vs. Conduction
This converter's units describe convective heat transfer — heat carried by a moving fluid touching a surface. That's a different physical mechanism from conduction, covered by the site's Thermal Conductivity Converter, which describes heat moving THROUGH a solid material. A complete heat-transfer calculation (like sizing a heat exchanger or predicting a building's heat loss) typically needs both: conduction through the walls or tube material, and convection at each fluid-contacted surface.
Example
A heat transfer coefficient of 25 W/(m²·K) equals 4.4027546 Btu/(h·ft²·°F). For scale, natural (unforced) air convection typically gives coefficients around 5-25 W/(m²·K), forced air convection (a fan) around 10-200 W/(m²·K), and forced water convection can reach 500-10,000 W/(m²·K) or higher.
Frequently Asked Questions
What's the difference between this and the Thermal Resistance Converter?
Heat transfer coefficient (this page) is a per-area rate — watts per square meter per degree. Thermal Resistance (a separate converter on this site) is a single-point figure without an area term — kelvin per watt — more suited to whole components like an electronics package. They're related but describe convection at a surface versus overall resistance of an object.
Why is water so much better than air at heat transfer?
Water has both a much higher density and specific heat capacity than air, and moving water carries far more thermal energy per unit volume than moving air for the same temperature rise — which translates directly into a much higher convective heat transfer coefficient, often 20-100 times greater for comparable flow conditions.
How accurate are these conversions?
Every conversion factor used here is the exact, internationally recognized relationship between the underlying power, area, and temperature units — results are limited only by floating-point display precision, not by rounded conversion constants.