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

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Live Conversion • ISO 80000-5:2019 Certified
1 BTU (IT)/hour/sq. foot = 0.00027796372 BTU (th)/second/sq. foot
1 Btu/(h·ft²) = 0.000277964 Btu/(s·ft²) • 1 Btu/(s·ft²) = 3597.591764 Btu/(h·ft²)
BTU (IT)/hour/sq. foot to BTU (th)/second/sq. foot: One BTU (IT)/hour/sq. foot is equal to 0.00027796372 Btus (th)/second/sq. foot.
Certified Authority Value
0.00027796
Btu/(s·ft²)
Exact: 1 Btu/(s·ft²) ≡ 3597.5917637496 Btu/(h·ft²)
Btu/(h·ft²)
Btu/(h·ft²)
Swap to BTU (th)/second/sq. foot to BTU (IT)/hour/sq. foot
Swap to BTU (th)/second/sq. foot to BTU (IT)/hour/sq. foot
Btu/(s·ft²)
Btu/(s·ft²) 0.00027796372
Quick Values:
Conversion Formula
To convert BTU (IT)/hour/sq. foot to BTU (th)/second/sq. foot, multiply by 0.00027796372
Btu/(h·ft²) × 0.00027796372 = Btu/(s·ft²)

Calculation: 1 Btu/(h·ft²) × 0.00027796372 = 0.00027796372 Btu/(s·ft²)

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

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

Tap any row to calculate
BTU (IT)/hour/sq. foot to BTU (th)/second/sq. foot: Primary Direct Table (15 Steps)
BTU (IT)/hour/sq. foot to BTU (th)/second/sq. foot Conversion Reference Table
Conversion & Equivalent Value Scientific Notation
0.001 Btu/(h·ft²) 2.779637 × 10⁻⁷ Btu/(s·ft²) 2.78 × 10⁻⁷
0.01 Btu/(h·ft²) 2.779637 × 10⁻⁶ Btu/(s·ft²) 2.78 × 10⁻⁶
0.1 Btu/(h·ft²) 2.779637 × 10⁻⁵ Btu/(s·ft²) 2.78 × 10⁻⁵
0.5 Btu/(h·ft²) 0.000138982 Btu/(s·ft²) 1.39 × 10⁻⁴
1 Btu/(h·ft²) 0.000277964 Btu/(s·ft²) 2.78 × 10⁻⁴
2 Btu/(h·ft²) 0.000555927 Btu/(s·ft²) 5.559 × 10⁻⁴
5 Btu/(h·ft²) 0.00138982 Btu/(s·ft²) 1.39 × 10⁻³
10 Btu/(h·ft²) 0.00277964 Btu/(s·ft²) 2.78 × 10⁻³
20 Btu/(h·ft²) 0.00555927 Btu/(s·ft²) 5.559 × 10⁻³
25 Btu/(h·ft²) 0.00694909 Btu/(s·ft²) 6.949 × 10⁻³
50 Btu/(h·ft²) 0.0138982 Btu/(s·ft²) 1.39 × 10⁻²
100 Btu/(h·ft²) 0.0277964 Btu/(s·ft²) 2.78 × 10⁻²
250 Btu/(h·ft²) 0.0694909 Btu/(s·ft²) 6.949 × 10⁻²
500 Btu/(h·ft²) 0.138982 Btu/(s·ft²) 1.39 × 10⁻¹
1000 Btu/(h·ft²) 0.277964 Btu/(s·ft²) 2.78 × 10⁻¹
BTU (th)/second/sq. foot to BTU (IT)/hour/sq. foot: Reciprocal Summary
BTU (th)/second/sq. foot to BTU (IT)/hour/sq. foot Conversion Reference Table
Reciprocal & Equivalent Value Scientific Notation
1 Btu/(s·ft²) 3597.591764 Btu/(h·ft²) 3.598 × 10³
5 Btu/(s·ft²) 17987.958819 Btu/(h·ft²) 1.799 × 10⁴
10 Btu/(s·ft²) 35975.917637 Btu/(h·ft²) 3.598 × 10⁴
50 Btu/(s·ft²) 179879.588187 Btu/(h·ft²) 1.799 × 10⁵
100 Btu/(s·ft²) 359759.176375 Btu/(h·ft²) 3.598 × 10⁵
View Complete 15-Row BTU (th)/second/sq. foot to BTU (IT)/hour/sq. foot 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/sq. foot (Btu/(h·ft²)) and BTU (th)/second/sq. foot (Btu/(s·ft²)):

BTU (IT)/hour/sq. foot References:

  • Solar constant extraterrestrial solar irradiance at top of atmosphere 431.43 Btu/(h·ft²)
  • Clear sky direct midday summer sunlight striking sea level ground 317 Btu/(h·ft²)
  • Human body resting thermal metabolic heat radiation to room 15.8499 Btu/(h·ft²)
  • Overcast winter day diffuse solar irradiance at sea level 31.6998 Btu/(h·ft²)

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

  • Solar constant extraterrestrial solar irradiance at top of atmosphere 0.119923 Btu/(s·ft²)
  • Clear sky direct midday summer sunlight striking sea level ground 0.088114 Btu/(s·ft²)
  • Human body resting thermal metabolic heat radiation to room 0.004406 Btu/(s·ft²)
  • Overcast winter day diffuse solar irradiance at sea level 0.008811 Btu/(s·ft²)

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

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

How to Convert BTU (IT)/hour/sq. foot to BTU (th)/second/sq. foot

Converting BTU (IT)/hour/sq. foot (Btu/(h·ft²)) to BTU (th)/second/sq. foot (Btu/(s·ft²)) is a core calculation in Heat Flux Density, which measures the rate of thermal energy transfer radiating or conducting through a unit area per second. 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/sq. foot equals 0.000277964 BTU (th)/second/sq. foot, while 1 Btu/(s·ft²) equals 3597.591764 Btu/(h·ft²).

Direct Factor1 Btu/(h·ft²) = 0.000277964 Btu/(s·ft²)
Inverse Ratio1 Btu/(s·ft²) = 3597.591764 Btu/(h·ft²)
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 (W/m²)) 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) = 3.154591 watt per square meter (W/m²)
2. Target SI Bridge (ktarget):1 Btu/(s·ft²) = 11348.93 watt per square meter (W/m²)
Step-by-step substitution for BTU (IT)/hour/sq. foot → BTU (th)/second/sq. foot:V(Btu/(s·ft²)) = V(Btu/(h·ft²)) × ( 3.154591 / 11348.93 ) = V(Btu/(h·ft²)) × 0.000277964
Mathematical FormulaValue in BTU (th)/second/sq. foot = Value in BTU (IT)/hour/sq. foot × 0.00027796372Direct computational formula applied for standard conversion.
Worked Example

Converting 75 Btu/(h·ft²) yields an exact output of 0.0208473 Btu/(s·ft²) in BTU (th)/second/sq. foot. Under higher industrial throughput, 240 Btu/(h·ft²) translates to 0.0667113 Btu/(s·ft²).

Inverse check: 1 Btu/(s·ft²) = 3597.591764 Btu/(h·ft²).

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

BTU (IT)/hour/sq. foot

Btu/(h·ft²)
Imperial / US

A BTU (IT)/hour/sq. foot (Btu/(h·ft²)) is an imperial and US customary unit for heat flux density.

Applications & Practical Context

In practical heat flux density terms, a solar constant extraterrestrial solar irradiance at top of atmosphere equals 431.43 Btu/(h·ft²), a clear sky direct midday summer sunlight striking sea level ground equals 317 Btu/(h·ft²), a human body resting thermal metabolic heat radiation to room equals 15.8499 Btu/(h·ft²).

Physical Setup

A physical magnitude of 1 Btu/(h·ft²) corresponds to 3.154591 W/m² in standard SI measurement.

Conversion to SI Unit: watt per square meter (W/m²)
1 Btu/(h·ft²) = 3.154591 W/m²

BTU (th)/second/sq. foot

Btu/(s·ft²)
Imperial / US

A BTU (th)/second/sq. foot (Btu/(s·ft²)) is an imperial and US customary unit for heat flux density.

Applications & Practical Context

In practical heat flux density terms, a solar constant extraterrestrial solar irradiance at top of atmosphere equals 0.119923 Btu/(s·ft²), a clear sky direct midday summer sunlight striking sea level ground equals 0.088114 Btu/(s·ft²), a human body resting thermal metabolic heat radiation to room equals 0.004406 Btu/(s·ft²).

Physical Setup

A physical magnitude of 1 Btu/(s·ft²) corresponds to 11348.93 W/m² in standard SI measurement.

Conversion to SI Unit: watt per square meter (W/m²)
1 Btu/(s·ft²) = 11348.93 W/m²

Domain Metrology & Engineering Applications

Governing Law & Equation

Thermal Transmission Flux (q = Q̇ / A)

Measurement Instrumentation

Rigorously quantified in laboratory and field settings using Schmidt-Boelter heat flux gauges, differential thermopile foil transducers, and calibrated Gardon radiant gauges.

Primary Industry Sectors

Applied across rocket nozzle combustion chamber analysis, fire resistance testing (ASTM E119), furnace wall heat loss auditing, and hypersonic aerothermal design under international metrology standard ISO 80000-5:2019, ASME PTC 19.3.

Institutional Metrology & Standard Authority:

Formulas, conversion coefficients, and base definitions on this page strictly adhere to the ISO 80000-5:2019, ASME PTC 19.3 and the BIPM SI Brochure (9th Edition). Governed by Thermal Transmission Flux (q = Q̇ / A) under ISO 80000 dimensional vector [M T⁻³].

Multi-Variable Engineering Bridge Thermal Radiation & Power Dissipation

Heat Flux Density to Total Thermal Power Bridge (Watts • Kilowatts • Megawatts • BTU/h • Horsepower)

Calculate total continuous heat dissipation power P = q" × A across surface barriers and exchangers, bridging heat flux density [M T⁻³] with thermal power [M L² T⁻³].

P = q" × A
Vector: [W/m²] × [m²] → [W]
Live Calculated Bridge Equivalent:
1 Btu/(h·ft²) at Industrial Hydronic Radiator Panel (8 m²) = 25.2367 W
Equals 0.02524 kW • 2.523673 × 10⁻⁵ MW • 0.03384 hp
SI Power
25.2367
W
Watts
Grid / Utility
0.02524
kW
Kilowatts
Power Plant
2.523673 × 10⁻⁵
MW
Megawatts
Mechanical Rating
0.03384
hp
Horsepower (Mechanical)
Metric Horsepower
0.03431
PS
Metric Horsepower (PS)
HVAC Thermal Rating
86.11
BTU/h
BTU per Hour
  1. 1. Normalize Input to SI Base Unit (W/m²):
    q" = 1 Btu/(h·ft²) × 3.15459083 = 3.15459083 W/m²
  2. 2. Apply Engineering Parameter (A):
    Selected condition: Industrial Hydronic Radiator Panel (8 m²) at A = 8 m²
  3. 3. Execute Governing Physical Law in SI Units:
    P = q" × A = (3.15459083 W/m²) × (8 m²) = 25.236727 W
  4. 4. Convert to Standard Engineering Units:
    • W: 25.236727 × 1 = 25.2367 W (Watts) • kW: 25.236727 × 0.001 = 0.02524 kW (Kilowatts) • MW: 25.236727 × 1 × 10⁻⁶ = 2.523673 × 10⁻⁵ MW (Megawatts) • hp: 25.236727 × 0.001341 = 0.03384 hp (Horsepower (Mechanical)) • PS: 25.236727 × 0.00136 = 0.03431 PS (Metric Horsepower (PS)) • BTU/h: 25.236727 × 3.4121 = 86.11 BTU/h (BTU per Hour)
Explore Full Power Converter →
Engineering Substance / Operating Standard Parameter Value (m²) Reference State / Condition Typical Industrial & Engineering Application
Residential Window Glazing (4 m²) 4 4.0 m² Double-pane exterior window glass aperture
Industrial Hydronic Radiator Panel (8 m²) 8 8.0 m² Convective space heating radiator surface
Shell & Tube Heat Exchanger (50 m²) 50 50.0 m² Industrial process fluid cooling bundle
Power Boiler Waterwall (200 m²) 200 200.0 m² Thermal power plant steam generator wall
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Frequently Asked Questions

There are exactly 0.00027796372 btus (th)/second/sq. foot (Btu/(s·ft²)) in 1 btu (it)/hour/sq. foot (Btu/(h·ft²)). To calculate larger amounts manually, simply multiply your total number of btus (it)/hour/sq. foot by the conversion multiplier of 0.00027796372.

The mathematical formula to convert btus (it)/hour/sq. foot to btus (th)/second/sq. foot is: [value] * 0.00027796372 = btus (th)/second/sq. foot. 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/sq. foot back to btus (it)/hour/sq. foot, you must divide your starting value by 0.00027796372. Our bidirectional tool automatically computes this inverse equation the moment you type into the btu (th)/second/sq. foot input field.

1 BTU (th)/second/sq. foot is larger than 1 BTU (IT)/hour/sq. foot. Specifically, 1 BTU (IT)/hour/sq. foot equals 0.00027796372 btus (th)/second/sq. foot, meaning 1 BTU (th)/second/sq. foot is 3597.5918 times larger than 1 BTU (IT)/hour/sq. foot (a difference of 3.56 orders of magnitude). Expressing measurements in btus (it)/hour/sq. foot requires a larger numerical value to represent the equivalent physical magnitude.

Under standard international measurement guidelines, 1 BTU (IT)/hour/sq. foot converts to 0.00027796372 btus (th)/second/sq. foot. Precise numerical conversion factors ensure consistency across laboratory, engineering, and field data.