Heat Transfer Coefficient converter
The U-value / film coefficient that links heat flux to temperature difference across a surface.
Converter
Quick pairs
tap to loadOne watt per square meter per kelvin in every heat transfer coefficient unit
4 rows| Unit | Symbol | 1 W/(m²·K) equals |
|---|---|---|
| Kilowatt per square meter per kelvin | kW/(m²·K) | 0.001 |
| Kilocalorie per hour per square meter per °C | kcal/(h·m²·°C) | 0.8604206501 |
| BTU per hour per square foot per °F | BTU/(h·ft²·°F) | 0.1761101837 |
| Calorie per second per square centimeter per °C | cal/(s·cm²·°C) | 2.390057361e-5 |
How the watt per square meter per kelvin to btu per hour per square foot per °f conversion works
The heat transfer coefficient (often called h, or the film coefficient) links heat flux to the temperature difference driving it, referenced here to watt per square meter per kelvin. Kilowatt per square meter per kelvin scales up by 1000 as expected. Kilocalorie per hour per square meter per °C and calorie per second per square centimeter per °C bring in the same calorie-based scaling (1.1622 and 41,840 respectively) seen throughout this unit group, reflecting older European and scientific-literature conventions. BTU per hour per square foot per °F, at roughly 5.678, is the standard imperial unit on US HVAC and heat-exchanger equipment.
The featured conversion is watt per square meter per kelvin to BTU per hour per square foot per °F: BTU/(h·ft²·°F) = W/(m²·K) × 0.1761101837. Reverse it by multiplying by 5.678263341.
Natural convection of still air against a wall, typically around 10 W/(m²·K), converts to 10 × 0.1761101837 ≈ 1.76 BTU/(h·ft²·°F). Forced convection with flowing water, which can reach roughly 500 W/(m²·K), converts to 500 × 0.1761101837 ≈ 88.06 BTU/(h·ft²·°F) — about 50 times higher, which is exactly why water-cooling systems outperform air-cooling for the same surface area.
This coefficient drives heat-exchanger sizing, building-envelope U-value calculations (the film coefficient is one term feeding into a wall's overall U-value), and electronics cooling design where engineers compare natural convection, forced-air, and liquid-cooling options for a given heatsink surface. HVAC designers use it to predict how quickly a duct, radiator, or coil transfers heat to the air or fluid moving past it.
The heat transfer coefficient is frequently confused with thermal conductivity from a different category, because both can appear in similar-looking W/(m·K)-style units and both show up in the same heat-transfer equations. The key difference: thermal conductivity (k) is a bulk material property independent of geometry, while the heat transfer coefficient (h) depends on the surface, the fluid flow conditions, and the geometry — the dimensionless Biot number in heat-transfer analysis exists specifically to compare the two and avoid conflating them.
Questions
How many BTU per hour per square foot per °F equal one watt per square meter per kelvin?
One W/(m²·K) equals 0.1761101837 BTU/(h·ft²·°F), the figure engineers reach for when comparing a metric convection coefficient to a US heat-exchanger spec.
Which units does this heat transfer coefficient converter cover?
5 units referenced to watt per square meter per kelvin: W/(m²·K), kW/(m²·K), kcal/(h·m²·°C), BTU/(h·ft²·°F), and cal/(s·cm²·°C).
How much precision is realistic for a heat transfer coefficient conversion?
The conversion factors are exact, but real convection coefficients depend heavily on flow velocity, surface roughness, and fluid properties, so measured or estimated h-values are rarely reliable beyond 2-3 significant figures regardless of how many decimals the converter shows.
When would I use kcal/(h·m²·°C) instead of W/(m²·K)?
Kilocalorie-based units still appear in some older European HVAC and process-engineering documentation; current international standards and most modern datasheets default to W/(m²·K).
Is the heat transfer coefficient the same as thermal conductivity?
No — thermal conductivity (k) is a fixed property of a material itself, while the heat transfer coefficient (h) describes how effectively heat moves between a surface and a moving fluid, and changes with flow speed, turbulence, and surface condition even for the same material.
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