Heat Flux Density Converter
Convert heat flux and irradiance between W/m², kW/m², W/cm², BTU/(h·ft²), kcal/(h·m²) and cal/(s·cm²).
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Result
Heat Flux Density units
Every unit below converts to every other one in the calculator. Values are relative to the base unit, the watt per square meter (W/m²).
| Unit | Symbol | System | Value |
|---|---|---|---|
| Watt per square meter | W/m² | SI | Base unit |
| Kilowatt per square meter | kW/m² | SI | = 1000 W/m² |
| Watt per square centimeter | W/cm² | SI | = 10000 W/m² |
| BTU per hour square foot | BTU/(h·ft²) | US customary | ≈ 3.154590745 W/m² |
| Kilocalorie (IT) per hour square meter | kcal/(h·m²) | metric | = 1.163 W/m² |
| Calorie (thermochemical) per second square centimeter | cal/(s·cm²) | CGS | = 41840 W/m² |
Watt per square meter quick reference
| Watt per square meter | BTU per hour square foot |
|---|---|
| 1 W/m² | ≈ 0.3169983306 BTU/(h·ft²) |
| 10 W/m² | ≈ 3.169983306 BTU/(h·ft²) |
| 100 W/m² | ≈ 31.69983306 BTU/(h·ft²) |
| 1000 W/m² | ≈ 316.9983306 BTU/(h·ft²) |
Among the 6 heat flux density units on this page, the smallest is the watt per square meter (W/m²) and the largest is the calorie (thermochemical) per second square centimeter (cal/(s·cm²)).
More heat flux density conversions
About heat flux density units
Heat flux density is the rate of heat flow through a unit area. Its SI unit is the watt per square meter (W/m²), the same unit used for solar irradiance. Full sunlight at ground level is roughly 1000 W/m².
One BTU/(h·ft²) is about 3.1546 W/m², and 1 W/m² is about 0.31700 BTU/(h·ft²). One kcal/(h·m²) using the IT kilocalorie is exactly 1.163 W/m², and one cal/(s·cm²) using the thermochemical calorie is exactly 41,840 W/m².
Frequently asked questions
- How do I convert W/m² to BTU/(h·ft²)?
- Multiply by about 0.316998. For example, 1000 W/m² is about 317 BTU/(h·ft²).
- Is heat flux the same as irradiance?
- They share the unit W/m². Irradiance is radiant power arriving at a surface, such as sunlight; heat flux density covers heat moving by any means, including conduction and convection.
- How many BTUs per hour square foot are in one watt per square meter?
- One watt per square meter ≈ 0.3169983306 BTU/(h·ft²) (BTUs per hour square foot).