Convert Btu (IT) per Second per Square Foot to Kilowatts per Square Meter
Btu (IT) per Second per Square Foot (Btu/(s·ft²)) to Kilowatt per Square Meter (kW/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/(s·ft²) = 11.35653 kW/m²
1 Btu (IT) per Second per Square Foot = 11.35653 Kilowatts per Square Meter
1 Kilowatt per Square Meter = 0.088055066 Btu (IT) per Second per Square Foot
1 Btu/(s·ft²) in every supported unit
Conversion chart: Btu (IT) per Second per Square Foot to Kilowatts per Square Meter
Conversion table
| Btu (IT) per Second per Square Foot (Btu/(s·ft²)) | Kilowatt per Square Meter (kW/m²) |
|---|---|
| 0.01 Btu/(s·ft²) | 0.1135653 kW/m² |
| 0.1 Btu/(s·ft²) | 1.135653 kW/m² |
| 1 Btu/(s·ft²) | 11.35653 kW/m² |
| 2 Btu/(s·ft²) | 22.71306 kW/m² |
| 3 Btu/(s·ft²) | 34.06959 kW/m² |
| 5 Btu/(s·ft²) | 56.78265 kW/m² |
| 10 Btu/(s·ft²) | 113.5653 kW/m² |
| 20 Btu/(s·ft²) | 227.1306 kW/m² |
| 50 Btu/(s·ft²) | 567.8265 kW/m² |
| 100 Btu/(s·ft²) | 1135.653 kW/m² |
| 1000 Btu/(s·ft²) | 11356.53 kW/m² |
Btu (IT) per Second per Square Foot (Btu/(s·ft²))
Definition: The same US customary heat flux concept as Btu per hour per square foot, but scaled to seconds for rapid or intense heat-transfer processes.
History: A natural time-unit variant used wherever heat-flow calculations need to match instantaneous, second-based power measurements rather than hourly building-scale rates.
Current use: Used in high-intensity US industrial process engineering, such as furnace and combustion heat-transfer calculations.
Kilowatt per Square Meter (kW/m²)
Definition: A larger-scale heat flux unit for high-intensity processes, where the base watt-per-square-meter figure would run into the thousands.
History: A straightforward SI multiple of watt per square meter, applied to concentrated heat sources like furnaces, welding arcs, and concentrated solar collectors.
Current use: Used in industrial furnace design, welding process specification, and concentrated solar power engineering.
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 Second per Square Foot → Kilowatt per Square Meter: multiply by 11.35653. For example, 1 Btu/(s·ft²) × 11.35653 = 11.35653 kW/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/(s·ft²) equals 11.35653 kW/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 Kilowatts per Square Meter are in 1 Btu (IT) per Second per Square Foot?
1 Btu (IT) per Second per Square Foot (Btu/(s·ft²)) equals exactly 11.35653 Kilowatts per Square Meter (kW/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.