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Btus (th)/second/sq. foot/°F to Btus (IT)/second/sq. foot/°F Converter (Btu (th)/(s·ft²·°F) to Btu/(s·ft²·°F))

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Live Conversion • ISO 80000-5:2019 Certified
1 BTU (th)/second/sq. foot/°F = 0.99933137 BTU (IT)/second/sq. foot/°F
1 Btu (th)/(s·ft²·°F) = 0.999331 Btu/(s·ft²·°F) • 1 Btu/(s·ft²·°F) = 1.000669 Btu (th)/(s·ft²·°F)
BTU (th)/second/sq. foot/°F to BTU (IT)/second/sq. foot/°F: One BTU (th)/second/sq. foot/°F is equal to 0.99933137 Btus (IT)/second/sq. foot/°F.
Certified Authority Value
0.99933137
Btu/(s·ft²·°F)
Exact: 1 Btu/(s·ft²·°F) ≡ 1.000669079 Btu (th)/(s·ft²·°F)
Btu (th)/(s·ft²·°F)
Btu (th)/(s·ft²·°F)
Swap to BTU (IT)/second/sq. foot/°F to BTU (th)/second/sq. foot/°F
Swap to BTU (IT)/second/sq. foot/°F to BTU (th)/second/sq. foot/°F
Btu/(s·ft²·°F)
Btu/(s·ft²·°F) 0.99933137
Quick Values:
Conversion Formula
To convert BTU (th)/second/sq. foot/°F to BTU (IT)/second/sq. foot/°F, multiply by 0.99933137
Btu (th)/(s·ft²·°F) × 0.99933137 = Btu/(s·ft²·°F)

Calculation: 1 Btu (th)/(s·ft²·°F) × 0.99933137 = 0.99933137 Btu/(s·ft²·°F)

Common BTU (th)/second/sq. foot/°F to BTU (IT)/second/sq. foot/°F Calculations

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

Tap any row to calculate
BTU (th)/second/sq. foot/°F to BTU (IT)/second/sq. foot/°F: Primary Direct Table (15 Steps)
BTU (th)/second/sq. foot/°F to BTU (IT)/second/sq. foot/°F Conversion Reference Table
Conversion & Equivalent Value Scientific Notation
0.001 Btu (th)/(s·ft²·°F) 0.000999331 Btu/(s·ft²·°F) 9.993 × 10⁻⁴
0.01 Btu (th)/(s·ft²·°F) 0.00999331 Btu/(s·ft²·°F) 9.993 × 10⁻³
0.1 Btu (th)/(s·ft²·°F) 0.0999331 Btu/(s·ft²·°F) 9.993 × 10⁻²
0.5 Btu (th)/(s·ft²·°F) 0.499666 Btu/(s·ft²·°F) 4.997 × 10⁻¹
1 Btu (th)/(s·ft²·°F) 0.999331 Btu/(s·ft²·°F) 9.993 × 10⁻¹
2 Btu (th)/(s·ft²·°F) 1.998663 Btu/(s·ft²·°F) 1.999 × 10⁰
5 Btu (th)/(s·ft²·°F) 4.996657 Btu/(s·ft²·°F) 4.997 × 10⁰
10 Btu (th)/(s·ft²·°F) 9.993314 Btu/(s·ft²·°F) 9.993 × 10⁰
20 Btu (th)/(s·ft²·°F) 19.986627 Btu/(s·ft²·°F) 1.999 × 10¹
25 Btu (th)/(s·ft²·°F) 24.983284 Btu/(s·ft²·°F) 2.498 × 10¹
50 Btu (th)/(s·ft²·°F) 49.966568 Btu/(s·ft²·°F) 4.997 × 10¹
100 Btu (th)/(s·ft²·°F) 99.933137 Btu/(s·ft²·°F) 9.993 × 10¹
250 Btu (th)/(s·ft²·°F) 249.832842 Btu/(s·ft²·°F) 2.498 × 10²
500 Btu (th)/(s·ft²·°F) 499.665684 Btu/(s·ft²·°F) 4.997 × 10²
1000 Btu (th)/(s·ft²·°F) 999.331368 Btu/(s·ft²·°F) 9.993 × 10²
BTU (IT)/second/sq. foot/°F to BTU (th)/second/sq. foot/°F: Reciprocal Summary
BTU (IT)/second/sq. foot/°F to BTU (th)/second/sq. foot/°F Conversion Reference Table
Reciprocal & Equivalent Value Scientific Notation
1 Btu/(s·ft²·°F) 1.000669 Btu (th)/(s·ft²·°F) 1.001 × 10⁰
5 Btu/(s·ft²·°F) 5.003345 Btu (th)/(s·ft²·°F) 5.003 × 10⁰
10 Btu/(s·ft²·°F) 10.006691 Btu (th)/(s·ft²·°F) 1.001 × 10¹
50 Btu/(s·ft²·°F) 50.033454 Btu (th)/(s·ft²·°F) 5.003 × 10¹
100 Btu/(s·ft²·°F) 100.066908 Btu (th)/(s·ft²·°F) 1.001 × 10²
View Complete 15-Row BTU (IT)/second/sq. foot/°F to BTU (th)/second/sq. 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 (th)/second/sq. foot/°F (Btu (th)/(s·ft²·°F)) and BTU (IT)/second/sq. foot/°F (Btu/(s·ft²·°F)):

BTU (th)/second/sq. foot/°F References:

  • Stationary ambient air natural free convection on vertical wall 0.000245 Btu (th)/(s·ft²·°F)
  • Forced air breeze blowing across automotive cooling radiator 0.002448 Btu (th)/(s·ft²·°F)
  • Liquid water forced circulation inside heat exchanger pipe 0.146857 Btu (th)/(s·ft²·°F)
  • Nucleate boiling heat transfer in pressurized steam boiler tube 0.734283 Btu (th)/(s·ft²·°F)

BTU (IT)/second/sq. foot/°F References:

  • Stationary ambient air natural free convection on vertical wall 0.000245 Btu/(s·ft²·°F)
  • Forced air breeze blowing across automotive cooling radiator 0.002446 Btu/(s·ft²·°F)
  • Liquid water forced circulation inside heat exchanger pipe 0.146758 Btu/(s·ft²·°F)
  • Nucleate boiling heat transfer in pressurized steam boiler tube 0.733792 Btu/(s·ft²·°F)

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

Converting BTU (th)/second/sq. foot/°F (Btu (th)/(s·ft²·°F)) to BTU (IT)/second/sq. foot/°F (Btu/(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 (th)/second/sq. foot/°F equals 0.999331 BTU (IT)/second/sq. foot/°F, while 1 Btu/(s·ft²·°F) equals 1.000669 Btu (th)/(s·ft²·°F).

Direct Factor1 Btu (th)/(s·ft²·°F) = 0.999331 Btu/(s·ft²·°F)
Inverse Ratio1 Btu/(s·ft²·°F) = 1.000669 Btu (th)/(s·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 (th)/(s·ft²·°F) = 20428.08 watt per square meter kelvin (W/(m²·K))
2. Target SI Bridge (ktarget):1 Btu/(s·ft²·°F) = 20441.748 watt per square meter kelvin (W/(m²·K))
Step-by-step substitution for BTU (th)/second/sq. foot/°F → BTU (IT)/second/sq. foot/°F:V(Btu/(s·ft²·°F)) = V(Btu (th)/(s·ft²·°F)) × ( 20428.08 / 20441.748 ) = V(Btu (th)/(s·ft²·°F)) × 0.999331
Mathematical FormulaValue in BTU (IT)/second/sq. foot/°F = Value in BTU (th)/second/sq. foot/°F × 0.99933137Direct computational formula applied for standard conversion.
Worked Example

Evaluating an input of 120 BTU (th)/second/sq. foot/°F (Btu (th)/(s·ft²·°F)) produces 119.919764 BTU (IT)/second/sq. foot/°F (Btu/(s·ft²·°F)). In heavy-duty utility and industrial workloads, 100 Btu (th)/(s·ft²·°F) equals 99.933137 Btu/(s·ft²·°F).

Inverse check: 1 Btu/(s·ft²·°F) = 1.000669 Btu (th)/(s·ft²·°F).

Understanding BTU (th)/second/sq. foot/°F and BTU (IT)/second/sq. foot/°F

BTU (th)/second/sq. foot/°F

Btu (th)/(s·ft²·°F)
Imperial / US

A BTU (th)/second/sq. 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 stationary ambient air natural free convection on vertical wall equals 0.000245 Btu (th)/(s·ft²·°F), a forced air breeze blowing across automotive cooling radiator equals 0.002448 Btu (th)/(s·ft²·°F), a liquid water forced circulation inside heat exchanger pipe equals 0.146857 Btu (th)/(s·ft²·°F).

Physical Setup

A physical magnitude of 1 Btu (th)/(s·ft²·°F) corresponds to 20428.08 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) = 20428.08 W/(m²·K)

BTU (IT)/second/sq. foot/°F

Btu/(s·ft²·°F)
Imperial / US

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

Applications & Practical Context

In practical heat transfer coefficient terms, a stationary ambient air natural free convection on vertical wall equals 0.000245 Btu/(s·ft²·°F), a forced air breeze blowing across automotive cooling radiator equals 0.002446 Btu/(s·ft²·°F), a liquid water forced circulation inside heat exchanger pipe equals 0.146758 Btu/(s·ft²·°F).

Physical Setup

A physical magnitude of 1 Btu/(s·ft²·°F) corresponds to 20441.748 W/(m²·K) in standard SI measurement.

Conversion to SI Unit: watt per square meter kelvin (W/(m²·K))
1 Btu/(s·ft²·°F) = 20441.748 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 (th)/(s·ft²·°F) at Forced Air Duct Cooling (ΔT = 25 K) = 510702 W/m²
Equals 510.702 kW/m² • 161891.7148 BTU/(h·ft²) • 12.197908 cal/(s·cm²)
SI Heat Flux
510702
W/m²
Watts per Square Meter
Solar / Combustion
510.702
kW/m²
Kilowatts per Square Meter
US Building Envelope
161891.7148
BTU/(h·ft²)
BTU per Hour Sq. Foot
CGS Thermal
12.197908
cal/(s·cm²)
Calories per Second Sq. Cm
Meteorology
732.0062
Ly/min
Langley per Minute
Furnace Flux
0.510702
MW/m²
Megawatts per Square Meter
  1. 1. Normalize Input to SI Base Unit (W/(m²·K)):
    h = 1 Btu (th)/(s·ft²·°F) × 20428.08 = 20428.08 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 = (20428.08 W/(m²·K)) × (25 K) = 510702 W/m²
  4. 4. Convert to Standard Engineering Units:
    • W/m²: 510702 × 1 = 510702 W/m² (Watts per Square Meter) • kW/m²: 510702 × 0.001 = 510.702 kW/m² (Kilowatts per Square Meter) • BTU/(h·ft²): 510702 × 0.317 = 161891.7148 BTU/(h·ft²) (BTU per Hour Sq. Foot) • cal/(s·cm²): 510702 × 2.3885 × 10⁻⁵ = 12.197908 cal/(s·cm²) (Calories per Second Sq. Cm) • Ly/min: 510702 × 0.001433 = 732.0062 Ly/min (Langley per Minute) • MW/m²: 510702 × 1 × 10⁻⁶ = 0.510702 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 0.99933137 btus (it)/second/sq. foot/°f (Btu/(s·ft²·°F)) in 1 btu (th)/second/sq. foot/°f (Btu (th)/(s·ft²·°F)). To calculate larger amounts manually, simply multiply your total number of btus (th)/second/sq. foot/°f by the conversion multiplier of 0.99933137.

The mathematical formula to convert btus (th)/second/sq. foot/°f to btus (it)/second/sq. foot/°f is: [value] * 0.99933137 = btus (it)/second/sq. 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 (it)/second/sq. foot/°f back to btus (th)/second/sq. foot/°f, you must divide your starting value by 0.99933137. Our bidirectional tool automatically computes this inverse equation the moment you type into the btu (it)/second/sq. foot/°f input field.

1 BTU (IT)/second/sq. foot/°F is larger than 1 BTU (th)/second/sq. foot/°F. Specifically, 1 BTU (th)/second/sq. foot/°F equals 0.99933137 btus (it)/second/sq. foot/°f, meaning 1 BTU (IT)/second/sq. foot/°F is 1.0007 times larger than 1 BTU (th)/second/sq. foot/°F (a difference of 0.00 orders of magnitude). Expressing measurements in btus (th)/second/sq. foot/°f requires a larger numerical value to represent the equivalent physical magnitude.

Under standard international measurement guidelines, 1 BTU (th)/second/sq. foot/°F converts to 0.99933137 btus (it)/second/sq. foot/°f. Precise numerical conversion factors ensure consistency across laboratory, engineering, and field data.