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Btus (IT)/hour/square foot/°F to Btus (th)/second/square foot/°F Converter (Btu/(h·ft²·°F) to Btu (th)/(s·ft²·°F))

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Live Conversion • ISO 80000-5:2019 Certified
1 Btu (IT)/hour/square foot/°F = 0.00027796264 Btu (th)/second/square foot/°F
1 Btu/(h·ft²·°F) = 0.000277963 Btu (th)/(s·ft²·°F) • 1 Btu (th)/(s·ft²·°F) = 3597.605818 Btu/(h·ft²·°F)
Btu (IT)/hour/square foot/°F to Btu (th)/second/square foot/°F: One Btu (IT)/hour/square foot/°F is equal to 0.00027796264 Btus (th)/second/square foot/°F.
Certified Authority Value
0.00027796
Btu (th)/(s·ft²·°F)
Exact: 1 Btu (th)/(s·ft²·°F) ≡ 3597.6058179441 Btu/(h·ft²·°F)
Btu/(h·ft²·°F)
Btu/(h·ft²·°F)
Swap to Btu (th)/second/square foot/°F to Btu (IT)/hour/square foot/°F
Swap to Btu (th)/second/square foot/°F to Btu (IT)/hour/square foot/°F
Btu (th)/(s·ft²·°F)
Btu (th)/(s·ft²·°F) 0.00027796264
Quick Values:
Conversion Formula
To convert Btu (IT)/hour/square foot/°F to Btu (th)/second/square foot/°F, multiply by 0.00027796264
Btu/(h·ft²·°F) × 0.00027796264 = Btu (th)/(s·ft²·°F)

Calculation: 1 Btu/(h·ft²·°F) × 0.00027796264 = 0.00027796264 Btu (th)/(s·ft²·°F)

Common Btu (IT)/hour/square foot/°F to Btu (th)/second/square foot/°F Calculations

Quick-lookup reference table showing calculated equivalents for standard increments between Btu (IT)/hour/square foot/°F (Btu/(h·ft²·°F)) and Btu (th)/second/square foot/°F (Btu (th)/(s·ft²·°F)).

Tap any row to calculate
Btu (IT)/hour/square foot/°F to Btu (th)/second/square foot/°F: Primary Direct Table (15 Steps)
Btu (IT)/hour/square foot/°F to Btu (th)/second/square foot/°F Conversion Reference Table
Conversion & Equivalent Value Scientific Notation
0.001 Btu/(h·ft²·°F) 2.779626 × 10⁻⁷ Btu (th)/(s·ft²·°F) 2.78 × 10⁻⁷
0.01 Btu/(h·ft²·°F) 2.779626 × 10⁻⁶ Btu (th)/(s·ft²·°F) 2.78 × 10⁻⁶
0.1 Btu/(h·ft²·°F) 2.779626 × 10⁻⁵ Btu (th)/(s·ft²·°F) 2.78 × 10⁻⁵
0.5 Btu/(h·ft²·°F) 0.000138981 Btu (th)/(s·ft²·°F) 1.39 × 10⁻⁴
1 Btu/(h·ft²·°F) 0.000277963 Btu (th)/(s·ft²·°F) 2.78 × 10⁻⁴
2 Btu/(h·ft²·°F) 0.000555925 Btu (th)/(s·ft²·°F) 5.559 × 10⁻⁴
5 Btu/(h·ft²·°F) 0.00138981 Btu (th)/(s·ft²·°F) 1.39 × 10⁻³
10 Btu/(h·ft²·°F) 0.00277963 Btu (th)/(s·ft²·°F) 2.78 × 10⁻³
20 Btu/(h·ft²·°F) 0.00555925 Btu (th)/(s·ft²·°F) 5.559 × 10⁻³
25 Btu/(h·ft²·°F) 0.00694907 Btu (th)/(s·ft²·°F) 6.949 × 10⁻³
50 Btu/(h·ft²·°F) 0.0138981 Btu (th)/(s·ft²·°F) 1.39 × 10⁻²
100 Btu/(h·ft²·°F) 0.0277963 Btu (th)/(s·ft²·°F) 2.78 × 10⁻²
250 Btu/(h·ft²·°F) 0.0694907 Btu (th)/(s·ft²·°F) 6.949 × 10⁻²
500 Btu/(h·ft²·°F) 0.138981 Btu (th)/(s·ft²·°F) 1.39 × 10⁻¹
1000 Btu/(h·ft²·°F) 0.277963 Btu (th)/(s·ft²·°F) 2.78 × 10⁻¹
Btu (th)/second/square foot/°F to Btu (IT)/hour/square foot/°F: Reciprocal Summary
Btu (th)/second/square foot/°F to Btu (IT)/hour/square foot/°F Conversion Reference Table
Reciprocal & Equivalent Value Scientific Notation
1 Btu (th)/(s·ft²·°F) 3597.605818 Btu/(h·ft²·°F) 3.598 × 10³
5 Btu (th)/(s·ft²·°F) 17988.02909 Btu/(h·ft²·°F) 1.799 × 10⁴
10 Btu (th)/(s·ft²·°F) 35976.058179 Btu/(h·ft²·°F) 3.598 × 10⁴
50 Btu (th)/(s·ft²·°F) 179880.290897 Btu/(h·ft²·°F) 1.799 × 10⁵
100 Btu (th)/(s·ft²·°F) 359760.581794 Btu/(h·ft²·°F) 3.598 × 10⁵
View Complete 15-Row Btu (th)/second/square foot/°F to Btu (IT)/hour/square foot/°F Table

Real-World Context & Everyday Benchmarks

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To help contextualize these units in everyday life, science, and engineering, here are verified real-world reference points for Btu (IT)/hour/square foot/°F (Btu/(h·ft²·°F)) and Btu (th)/second/square foot/°F (Btu (th)/(s·ft²·°F)):

Btu (IT)/hour/square foot/°F References:

  • Standard modern residential double-pane window U-factor 0.28 Btu/(h·ft²·°F)
  • Still interior air film natural convection on drywall surface 1.46 Btu/(h·ft²·°F)
  • Winter 15 mph wind exterior building wall surface air film 6 Btu/(h·ft²·°F)

Btu (th)/second/square foot/°F References:

  • High-pressure steam boiler water-wall tube boiling coefficient 0.5 Btu (th)/(s·ft²·°F)

Tap any benchmark above to automatically calculate its exact equivalent in Btu (th)/second/square foot/°F.

ISQ Dimension: [M T⁻³ Θ⁻¹] Coherent SI Unit: watt per square meter kelvin (W/(m²·K)) Thermodynamics & Heat Transfer

How to Convert Btu (IT)/hour/square foot/°F to Btu (th)/second/square foot/°F

Converting Btu (IT)/hour/square foot/°F (Btu/(h·ft²·°F)) to Btu (th)/second/square foot/°F (Btu (th)/(s·ft²·°F)) is a core calculation in Heat Transfer Coefficient, which quantifies the proportionality constant between the heat flux and the thermodynamic driving temperature difference. This calculation navigates the boundary between the International Metric System (SI) and British Imperial / US Customary engineering standards. In contemporary metrology, Imperial units are defined in terms of exact SI standards via international agreements—notably NIST SP 811 and the 1959 International Yard and Pound Agreement. Exactly 1 Btu (IT)/hour/square foot/°F equals 0.000277963 Btu (th)/second/square foot/°F, while 1 Btu (th)/(s·ft²·°F) equals 3597.605818 Btu/(h·ft²·°F).

Direct Factor1 Btu/(h·ft²·°F) = 0.000277963 Btu (th)/(s·ft²·°F)
Inverse Ratio1 Btu (th)/(s·ft²·°F) = 3597.605818 Btu/(h·ft²·°F)
Conversion ScaleMetric SI to British Imperial / US Customary Bridge
First-Principles SI Derivation ProofNIST SP 811 / ISO 80000 Compliance

Mathematical Conversion Derivation via Coherent SI Base Unit

Under the International System of Quantities (ISQ), dimensional conversion between non-SI units is rigorously resolved by bridging through the coherent SI base unit (watt per square meter kelvin (W/(m²·K))) without arbitrary rounding:

Vtarget=Vsource×(ksource→SIktarget→SI)V_{\text{target}} = V_{\text{source}} \times \left( \frac{k_{\text{source} \to \text{SI}}}{k_{\text{target} \to \text{SI}}} \right)
Universal Dimensional Conversion Law (ISO 80000 / NIST SP 811)
1. Source SI Bridge (ksource):1 Btu/(h·ft²·°F) = 5.678269 watt per square meter kelvin (W/(m²·K))
2. Target SI Bridge (ktarget):1 Btu (th)/(s·ft²·°F) = 20428.174538 watt per square meter kelvin (W/(m²·K))
Step-by-step substitution for Btu (IT)/hour/square foot/°F → Btu (th)/second/square foot/°F:V(Btu (th)/(s·ft²·°F)) = V(Btu/(h·ft²·°F)) × ( 5.678269 / 20428.174538 ) = V(Btu/(h·ft²·°F)) × 0.000277963
Mathematical FormulaValue in Btu (th)/second/square foot/°F = Value in Btu (IT)/hour/square foot/°F × 0.00027796264Direct computational formula applied for standard conversion.
Worked Example

For an engineering input of 36 Btu/(h·ft²·°F), applying the conversion factor yields exactly 0.0100067 Btu (th)/(s·ft²·°F). At larger operational scale, 2500 Btu (IT)/hour/square foot/°F corresponds to 0.694907 Btu (th)/(s·ft²·°F).

Inverse check: 1 Btu (th)/(s·ft²·°F) = 3597.605818 Btu/(h·ft²·°F).

Understanding Btu (IT)/hour/square foot/°F and Btu (th)/second/square foot/°F

Btu (IT)/hour/square foot/°F

Btu/(h·ft²·°F)
Imperial / US

A Btu (IT)/hour/square foot/°F (Btu/(h·ft²·°F)) is an imperial and US customary unit for heat transfer coefficient.

Applications & Practical Context

In practical heat transfer coefficient terms, a standard modern residential double-pane window U-factor equals 0.28 Btu/(h·ft²·°F), a still interior air film natural convection on drywall surface equals 1.46 Btu/(h·ft²·°F), a winter 15 mph wind exterior building wall surface air film equals 6 Btu/(h·ft²·°F).

Physical Setup

A physical magnitude of 1 Btu/(h·ft²·°F) corresponds to 5.678269 W/(m²·K) in standard SI measurement.

Conversion to SI Unit: watt per square meter kelvin (W/(m²·K))
1 Btu/(h·ft²·°F) = 5.678269 W/(m²·K)

Btu (th)/second/square foot/°F

Btu (th)/(s·ft²·°F)
Imperial / US

A Btu (th)/second/square foot/°F (Btu (th)/(s·ft²·°F)) is an imperial and US customary unit for heat transfer coefficient.

Applications & Practical Context

In practical heat transfer coefficient terms, a high-pressure steam boiler water-wall tube boiling coefficient equals 0.5 Btu (th)/(s·ft²·°F).

Physical Setup

A physical magnitude of 1 Btu (th)/(s·ft²·°F) corresponds to 20428.174538 W/(m²·K) in standard SI measurement.

Conversion to SI Unit: watt per square meter kelvin (W/(m²·K))
1 Btu (th)/(s·ft²·°F) = 20428.174538 W/(m²·K)

Domain Metrology & Engineering Applications

Governing Law & Equation

Newton's Law of Cooling (q = h · ΔT)

Measurement Instrumentation

Rigorously quantified in laboratory and field settings using surface heat flux transducer plates coupled with surface RTD arrays, and wind tunnel boundary layer calorimeters.

Primary Industry Sectors

Applied across industrial heat exchanger rating, nuclear reactor cooling loop simulation, electronics forced-air cooling, and architectural U-value certification under international metrology standard ISO 80000-5:2019, ASME PTC.

Institutional Metrology & Standard Authority:

Formulas, conversion coefficients, and base definitions on this page strictly adhere to the ISO 80000-5:2019, ASME PTC and the BIPM SI Brochure (9th Edition). Governed by Newton's Law of Cooling (q = h · ΔT) under ISO 80000 dimensional vector [M T⁻³ Θ⁻¹].

Multi-Variable Engineering Bridge Convective Thermodynamics & Cooling

Heat Transfer Coefficient to Convective Flux Bridge (W/m² • kW/m² • BTU/(h·ft²) • cal/(s·cm²))

Calculate Newton’s law of cooling convective heat flux q" = h × ΔT across convective film temperature drops, bridging heat transfer coefficient [M T⁻³ Θ⁻¹] with heat flux [M T⁻³].

q" = h × ΔT
Vector: [W/(m²·K)] × [K] → [W/m²]
Live Calculated Bridge Equivalent:
1 Btu/(h·ft²·°F) at Forced Air Duct Cooling (ΔT = 25 K) = 141.9567 W/m²
Equals 0.142 kW/m² • 45.0001 BTU/(h·ft²) • 0.00339058 cal/(s·cm²)
SI Heat Flux
141.9567
W/m²
Watts per Square Meter
Solar / Combustion
0.142
kW/m²
Kilowatts per Square Meter
US Building Envelope
45.0001
BTU/(h·ft²)
BTU per Hour Sq. Foot
CGS Thermal
0.00339058
cal/(s·cm²)
Calories per Second Sq. Cm
Meteorology
0.2035
Ly/min
Langley per Minute
Furnace Flux
0.00014196
MW/m²
Megawatts per Square Meter
  1. 1. Normalize Input to SI Base Unit (W/(m²·K)):
    h = 1 Btu/(h·ft²·°F) × 5.67826926 = 5.67826926 W/(m²·K)
  2. 2. Apply Engineering Parameter (ΔT):
    Selected condition: Forced Air Duct Cooling (ΔT = 25 K) at ΔT = 25 K
  3. 3. Execute Governing Physical Law in SI Units:
    q" = h × ΔT = (5.67826926 W/(m²·K)) × (25 K) = 141.956732 W/m²
  4. 4. Convert to Standard Engineering Units:
    • W/m²: 141.956732 × 1 = 141.9567 W/m² (Watts per Square Meter) • kW/m²: 141.956732 × 0.001 = 0.142 kW/m² (Kilowatts per Square Meter) • BTU/(h·ft²): 141.956732 × 0.317 = 45.0001 BTU/(h·ft²) (BTU per Hour Sq. Foot) • cal/(s·cm²): 141.956732 × 2.3885 × 10⁻⁵ = 0.00339058 cal/(s·cm²) (Calories per Second Sq. Cm) • Ly/min: 141.956732 × 0.001433 = 0.2035 Ly/min (Langley per Minute) • MW/m²: 141.956732 × 1 × 10⁻⁶ = 0.00014196 MW/m² (Megawatts per Square Meter)
Explore Full Heat Flux Density Converter →
Engineering Substance / Operating Standard Parameter Value (K) Reference State / Condition Typical Industrial & Engineering Application
Natural Air Convection (ΔT = 15 K) 15 ΔT = 15 K (15°C) Still room air room heating surface delta
Forced Air Duct Cooling (ΔT = 25 K) 25 ΔT = 25 K (25°C) Forced fan ventilation heatsink airflow
Forced Liquid Water Cooling (ΔT = 30 K) 30 ΔT = 30 K Pumped liquid cold plate or engine jacket
Nucleate Boiling Heat Transfer (ΔT = 50 K) 50 ΔT = 50 K Boiler evaporator tube wall boundary
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Frequently Asked Questions

There are exactly 0.00027796264 btus (th)/second/square foot/°f (Btu (th)/(s·ft²·°F)) in 1 btu (it)/hour/square foot/°f (Btu/(h·ft²·°F)). To calculate larger amounts manually, simply multiply your total number of btus (it)/hour/square foot/°f by the conversion multiplier of 0.00027796264.

The mathematical formula to convert btus (it)/hour/square foot/°f to btus (th)/second/square foot/°f is: [value] * 0.00027796264 = btus (th)/second/square foot/°f. Rather than doing the math manually, you can use our high-precision online calculator to process this exact equation instantly without rounding errors.

To perform the reverse calculation from btus (th)/second/square foot/°f back to btus (it)/hour/square foot/°f, you must divide your starting value by 0.00027796264. Our bidirectional tool automatically computes this inverse equation the moment you type into the btu (th)/second/square foot/°f input field.

1 Btu (th)/second/square foot/°F is larger than 1 Btu (IT)/hour/square foot/°F. Specifically, 1 Btu (IT)/hour/square foot/°F equals 0.00027796264 btus (th)/second/square foot/°f, meaning 1 Btu (th)/second/square foot/°F is 3597.6058 times larger than 1 Btu (IT)/hour/square foot/°F (a difference of 3.56 orders of magnitude). Expressing measurements in btus (it)/hour/square foot/°f requires a larger numerical value to represent the equivalent physical magnitude.

Under standard international measurement guidelines, 1 Btu (IT)/hour/square foot/°F converts to 0.00027796264 btus (th)/second/square foot/°f. Precise numerical conversion factors ensure consistency across laboratory, engineering, and field data.