Convert watt/square metre to btu (it)/hour/square foot

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Watt/Square Metre

The watt per square metre (W/m²) is the SI unit of heat flux density and irradiance. It represents the power transmitted per unit area. The solar constant (total solar irradiance) at Earth's orbit is approximately 1361 W/m². Used in heat transfer engineering, solar energy, and thermal radiation analysis. 


Btu (IT)/Hour/Square Foot

The British thermal unit (IT) per hour per square foot (Btu/(h·ft²)) equals approximately 3.155 W/m² and is the most common imperial unit of heat flux in North American HVAC and building engineering. It is used for heat loss calculations, U-values, and thermal performance ratings of building envelopes. 


Watt/Square Metre to Btu (IT)/Hour/Square Foot conversion table
Watt/Square MetreBtu (IT)/Hour/Square FootBtu (IT)/Hour/Square FootWatt/Square Metre
10.31699813.15459
20.63399726.30918
30.95099539.46377
51.58499515.773
103.169981031.5459
206.339972063.0918
257.924962578.8648
5015.849950157.73
10031.6998100315.459
25079.2496250788.648
500158.4995001577.3
1000316.99810003154.59
How to convert Watt/Square Metre to Btu (IT)/Hour/Square Foot

1 W/m² = 0.316998 Btu/(h·ft²). To convert any value, multiply it by 0.316998. For example, 25 W/m² = 7.92496 Btu/(h·ft²).

Frequently asked questions
How many Btu/(h·ft²) are there in one W/m²?
One W/m² is equal to 0.316998 Btu/(h·ft²).
How do you convert Watt/Square Metre to Btu (IT)/Hour/Square Foot?
Multiply the value in Watt/Square Metre by 0.316998 to get the result in Btu (IT)/Hour/Square Foot.
How much is 25 W/m² in Btu/(h·ft²)?
25 W/m² is equal to 7.92496 Btu/(h·ft²).
How do you convert Btu (IT)/Hour/Square Foot back to Watt/Square Metre?
Divide by the same factor: multiply the value in Btu (IT)/Hour/Square Foot by 3.15459 to get Watt/Square Metre.

Most common heat flux density unit conversions