About this converter
The heat transfer coefficient (U or h) quantifies how effectively heat moves from a fluid to a solid surface — or across a composite wall — per unit area and per degree of temperature difference. The SI unit is watt per square metre per kelvin (W/m²·K). A higher coefficient means faster heat transfer for the same temperature difference and surface area.
HVAC engineers, heat exchanger designers, and building energy analysts work with heat transfer coefficients daily, but in different unit systems. European standards use W/m²·K; US industrial codes use Btu/h·ft²·°F; older European building codes use kcal/h·m²·°C. Converting accurately between these is essential when comparing equipment specifications, sizing condensers and evaporators, or applying ASHRAE standards to metric-designed systems.
How to Use This Converter
- Enter the heat transfer coefficient value in the Value field.
- Select the source unit from the From dropdown.
- Select the target unit from the To dropdown.
- Read the converted result and formula line.
- Use Swap to compare SI and imperial specifications.
Units Covered
| Unit | Symbol | Common Use |
|---|---|---|
| Watt/m²·K | W/m²·K | SI standard; used in European engineering and all scientific publications. |
| Watt/m²·°C | W/m²·°C | Same magnitude as W/m²·K; used in building energy codes. |
| J/s·m²·K | J/s·m²·K | Equivalent to W/m²·K; used in thermodynamics textbooks. |
| kcal(IT)/h·m²·°C | kcal/h·m²·°C | Older European HVAC and chemical process engineering. |
| kcal(IT)/h·ft²·°C | kcal/h·ft²·°C | Mixed-unit systems in legacy petrochemical plants. |
| Btu(IT)/h·ft²·°F | Btu/h·ft²·°F | Standard US engineering; ASHRAE handbooks and TEMA shell-and-tube specs. |
| Btu(th)/h·ft²·°F | Btu(th)/h·ft²·°F | Thermochemical Btu variant; ~0.07% lower than IT Btu. |
| CHU/h·ft²·°C | CHU/h·ft²·°C | UK legacy unit (Celsius Heat Unit); 1 CHU/h/ft²/°C = 5.678 W/m²·K. |
W/m²·K to Btu/h·ft²·°F Conversion Table
| From | To |
|---|---|
| 1 W/m²·K | 0.1761 Btu/h·ft²·°F |
| 5 W/m²·K | 0.8806 Btu/h·ft²·°F |
| 10 W/m²·K | 1.761 Btu/h·ft²·°F |
| 20 W/m²·K | 3.522 Btu/h·ft²·°F |
| 50 W/m²·K | 8.806 Btu/h·ft²·°F |
| 100 W/m²·K | 17.61 Btu/h·ft²·°F |
| 200 W/m²·K | 35.22 Btu/h·ft²·°F |
| 500 W/m²·K | 88.06 Btu/h·ft²·°F |
| 1000 W/m²·K | 176.1 Btu/h·ft²·°F |
| 5000 W/m²·K | 880.6 Btu/h·ft²·°F |
How to Convert W/m²·K to Btu/h·ft²·°F
W/m²·K to Btu/h·ft²·°F
For example, 50 W/m²·K × 0.17611 = 8.806 Btu/h·ft²·°F — a typical forced air-to-air heat exchanger coefficient.
Btu/h·ft²·°F to W/m²·K
For example, 1 Btu/h·ft²·°F × 5.6783 = 5.678 W/m²·K — the standard conversion factor for ASHRAE-to-EN comparisons.
When You Need to Convert Heat Transfer Coefficients
HVAC engineers sizing air-handling units compare manufacturer datasheets in Btu/h·ft²·°F (US suppliers) and W/m²·K (European suppliers). A chilled-water coil rated at 10 Btu/h·ft²·°F equals 56.8 W/m²·K. Converting accurately ensures that coils selected from different catalogues deliver the same thermal performance before ordering.
Heat exchanger engineers designing shell-and-tube condensers use TEMA standards (imperial) alongside process simulation software outputs (SI). An overall heat transfer coefficient of 300 W/m²·K must be entered as 52.8 Btu/h·ft²·°F when filling in TEMA specification sheets. Errors at this conversion step can cause under-sized heat exchangers that fail to meet process duty requirements.
Building envelope designers assess U-values for fenestration and insulation panels. ASHRAE 90.1 sets maximum U-values in Btu/h·ft²·°F while EN 673 uses W/m²·K. A triple-glazed unit with U = 0.18 Btu/h·ft²·°F = 1.022 W/m²·K — converting this correctly is essential for demonstrating code compliance when submitting energy models for building permit approval in either jurisdiction.