Heat Transfer Coefficient Converter

Convert heat transfer coefficients and U-values between W/(m²·K), BTU/(h·ft²·°F), kcal/(h·m²·°C) and other units.

How to use the Heat Transfer Coefficient Converter

  1. Type the value you want to convert in the first box.
  2. Choose the unit you are converting from and the unit you want to convert to.
  3. Read the result instantly. Use the swap button to reverse the direction, or copy the result with one click.

Popular heat transfer coefficient conversions

ConversionResultFormula
Watts per square meter kelvin to BTU per hour square foot °F1 W/(m²·K) = 0.17611 BTU/(h·ft²·°F)BTU per hour square foot °F = watts per square meter kelvin × 0.17611018
BTU per hour square foot °F to watts per square meter kelvin1 BTU/(h·ft²·°F) = 5.67826 W/(m²·K)watts per square meter kelvin = BTU per hour square foot °F × 5.6782633

Supported heat transfer coefficient units

UnitSymbolEqual to
Watt per square meter kelvinW/(m²·K)1 W/(m²·K)
Kilowatt per square meter kelvinkW/(m²·K)1,000 W/(m²·K)
Watt per square centimeter kelvinW/(cm²·K)10,000 W/(m²·K)
BTU per hour square foot °FBTU/(h·ft²·°F)5.6782633 W/(m²·K)
Kilocalorie per hour square meter °Ckcal/(h·m²·°C)1.163 W/(m²·K)
Calorie per second square centimeter °Ccal/(s·cm²·°C)41,868 W/(m²·K)

Heat transfer coefficient and U-value

The heat transfer coefficient tells you how much heat flows through one unit of area for each degree of temperature difference. In building physics it is called the U-value: the lower the U-value, the better a wall, window or roof insulates.

Heat flow is calculated as Q = U × A × ΔT. A window with U = 1.4 W/(m²·K), area 2 m² and a 20 K temperature difference loses 1.4 × 2 × 20 = 56 W.

US practice uses BTU/(h·ft²·°F) and often quotes the inverse, the R-value. To convert a US U-value to SI, multiply by 5.678.

Frequently asked questions

How do I convert BTU/(h·ft²·°F) to W/(m²·K)?

Multiply by 5.678263. For example, a U-value of 0.30 BTU/(h·ft²·°F) is about 1.70 W/(m²·K).

Is W/(m²·K) the same as W/(m²·°C)?

Yes. A temperature difference of one kelvin is the same size as one degree Celsius.

What is the relationship between U-value and R-value?

They are inverses: U = 1 ÷ R. A higher R-value or a lower U-value means better insulation.

Related tools