Convert Btu (IT) per Hour per Square Foot to Kilocalories (IT) per Hour per Square Meter
Btu (IT) per Hour per Square Foot (Btu/(h·ft²)) to Kilocalorie (IT) per Hour per Square Meter (kcal/(h·m²)) heat flux density conversion — enter any value below to get an instant result, or use the table for common values.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 Btu/(h·ft²) = 2.7124678 kcal/(h·m²)
1 Btu (IT) per Hour per Square Foot = 2.7124678 Kilocalories (IT) per Hour per Square Meter
1 Kilocalorie (IT) per Hour per Square Meter = 0.36866798 Btu (IT) per Hour per Square Foot
1 Btu/(h·ft²) in every supported unit
Conversion chart: Btu (IT) per Hour per Square Foot to Kilocalories (IT) per Hour per Square Meter
Conversion table
| Btu (IT) per Hour per Square Foot (Btu/(h·ft²)) | Kilocalorie (IT) per Hour per Square Meter (kcal/(h·m²)) |
|---|---|
| 0.01 Btu/(h·ft²) | 0.027124678 kcal/(h·m²) |
| 0.1 Btu/(h·ft²) | 0.27124678 kcal/(h·m²) |
| 1 Btu/(h·ft²) | 2.7124678 kcal/(h·m²) |
| 2 Btu/(h·ft²) | 5.4249355 kcal/(h·m²) |
| 3 Btu/(h·ft²) | 8.1374033 kcal/(h·m²) |
| 5 Btu/(h·ft²) | 13.562339 kcal/(h·m²) |
| 10 Btu/(h·ft²) | 27.124678 kcal/(h·m²) |
| 20 Btu/(h·ft²) | 54.249355 kcal/(h·m²) |
| 50 Btu/(h·ft²) | 135.62339 kcal/(h·m²) |
| 100 Btu/(h·ft²) | 271.24678 kcal/(h·m²) |
| 1000 Btu/(h·ft²) | 2712.4678 kcal/(h·m²) |
Btu (IT) per Hour per Square Foot (Btu/(h·ft²))
Definition: The standard US customary heat flux unit — British thermal units passing through one square foot of surface, per hour.
History: Built from the Btu, hour, and square foot, all standard US construction and HVAC measurements, giving American building engineers a heat-flow-rate unit matching everyday design calculations.
Current use: The standard unit for building heat-gain and heat-loss calculations in US HVAC engineering, printed throughout ASHRAE design guides and load-calculation software.
Kilocalorie (IT) per Hour per Square Meter (kcal/(h·m²))
Definition: A metric heat flux unit combining the kilocalorie and hour, historically common in European heat-transfer engineering before SI watts fully took over.
History: Reflects the calorie-based heat-engineering tradition used across continental Europe through much of the 20th century.
Current use: Occasionally still seen in older European HVAC and industrial heat-transfer documentation.
Supported Units
| Unit | Symbol | In W/m² |
|---|---|---|
| Watt per Square Meter | W/m² | 1 W/m² |
| Kilowatt per Square Meter | kW/m² | 1000 W/m² |
| Watt per Square Centimeter | W/cm² | 10000 W/m² |
| Watt per Square Inch | W/in² | 1550.0031 W/m² |
| Kilocalorie (IT) per Hour per Square Meter | kcal/(h·m²) | 1.163 W/m² |
| Calorie (IT) per Second per Square Centimeter | cal/(s·cm²) | 41868 W/m² |
| Btu (IT) per Hour per Square Foot | Btu/(h·ft²) | 3.1546 W/m² |
| Btu (IT) per Second per Square Foot | Btu/(s·ft²) | 11356.53 W/m² |
| Horsepower per Square Foot | hp/ft² | 8026.65 W/m² |
| Foot Pound per Minute per Square Foot | ft·lb/(min·ft²) | 0.2432 W/m² |
About These Parameters
- Value
- The heat flux density value you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The unit your input value is currently measured in — a solar spec sheet's W/m², or a US HVAC load calculation's Btu/(h·ft²).
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly.
How Heat Flux Density Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to watts per square meter. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Btu (IT) per Hour per Square Foot → Kilocalorie (IT) per Hour per Square Meter: multiply by 2.7124678. For example, 1 Btu/(h·ft²) × 2.7124678 = 2.7124678 kcal/(h·m²).
Solar Irradiance
"1,000 W/m²" is the standard reference solar irradiance used to rate solar panels under laboratory "Standard Test Conditions" — roughly what a clear, midday sun delivers to a surface facing directly toward it. Real-world irradiance varies constantly with time of day, cloud cover, and season, which is why a panel's rated wattage (measured at that fixed 1,000 W/m² reference) rarely matches its actual output at any given moment.
Heat Flux Density vs. Heat Density
This page's units are all RATES (power per area, e.g. watts per square meter) — how fast energy is moving right now. The site's separate Heat Density Converter covers the cumulative TOTAL (energy per area, e.g. joules per square meter) — how much energy has landed altogether over some period. Multiplying a heat flux density by a duration of time gives you a heat density, the same relationship speed has to distance.
Example
A heat flux density of 1 Btu/(h·ft²) equals 2.7124678 kcal/(h·m²). For scale, peak midday solar irradiance is around 1,000 W/m² (about 317 Btu/(h·ft²)), while a typical well-insulated wall might lose heat at only a few W/m² on a cold day.
Frequently Asked Questions
How many Kilocalories (IT) per Hour per Square Meter are in 1 Btu (IT) per Hour per Square Foot?
1 Btu (IT) per Hour per Square Foot (Btu/(h·ft²)) equals exactly 2.7124678 Kilocalories (IT) per Hour per Square Meter (kcal/(h·m²)).
Why does this page have so many units compared to other converters?
Heat flux density is used across an unusually wide range of fields — solar engineering, HVAC, laser physics, industrial heating, and classical thermodynamics — each of which historically settled on its own preferred combination of energy, time, and area units, so this page collects the most commonly seen ones from each.
What's a normal heat flux density value for solar panels?
Solar panels are rated at a standard 1,000 W/m² reference irradiance, but real-world sunlight typically ranges from near 0 (night, heavy cloud) up to around 1,000-1,100 W/m² at clear-sky, high-sun conditions, varying with latitude, season, and time of day.
How accurate are these conversions?
Every conversion factor used here is the exact, internationally recognized relationship between the underlying power, energy, and area units — results are limited only by floating-point display precision, not by rounded conversion constants.