Convert Watts per Square Meter to BTU per Hour-Square Foot
Instantly convert Watts per Square Meter (W/m²) to BTU per Hour-Square Foot (BTU/(hr·ft²)) with our free online calculator.
Formula: W/m² to BTU/(hr·ft²) — multiply by 0.316998
Reference Table
| Watts per Square Meter (W/m²) | BTU per Hour-Square Foot (BTU/(hr·ft²)) |
|---|---|
| 1 | 0.316998 |
| 5 | 1.58499 |
| 10 | 3.16998 |
| 25 | 7.92496 |
| 50 | 15.8499 |
| 100 | 31.6998 |
How to Convert Watts per Square Meter to BTU per Hour-Square Foot
Formula
To convert Watts per Square Meter (W/m²) to BTU per Hour-Square Foot (BTU/(hr·ft²)): multiply by 0.316998
Step-by-Step
- Start with your value in Watts per Square Meter (W/m²).
- Multiply by 0.316998 to perform the conversion.
- The result is your value expressed in BTU per Hour-Square Foot (BTU/(hr·ft²)).
Conversion Factor
1 W/m² = 0.316998 BTU/(hr·ft²)
Reverse Factor
1 BTU/(hr·ft²) = 3.15459 W/m²
Worked Example
Convert 25 Watts per Square Meter to BTU per Hour-Square Foot: 25 W/m² = 7.92496 BTU/(hr·ft²)
About Watt per Square Meter (W/m²)
The SI unit of heat flux density (ISO 80000-5 §5-10) — the rate of heat-energy flow per unit area perpendicular to the flow direction. W/m² is the universal working unit in heat-transfer analysis (Fourier conduction q = −k·∇T, Newton's law of cooling q = h·ΔT, Stefan-Boltzmann radiation q = ε·σ·T⁴), solar-energy and atmospheric science, building-envelope thermal modeling, electronics cooling, and radiation intensity. Reference values: the solar constant at Earth's top of atmosphere is exactly 1,361 W/m² (the standard reference value defined by IAU 2015 Resolution B3 / SORCE TIM instrument data); a clear-sky noon at sea level ~1,000 W/m² (the standard test condition for photovoltaic module rating per IEC 61215); average daily Earth-surface insolation 150-250 W/m² (region-dependent); human body emits ~75-100 W/m² as black-body IR radiation at skin temperature; CMB cosmic microwave background ~3.13 × 10⁻⁶ W/m² at 2.725 K. Building-envelope U-factors (W/(m²·K)) multiplied by ΔT yield heat flux in W/m². Also the SI unit for irradiance, sound intensity (in acoustics), and Poynting-vector electromagnetic flux.
About BTU per Hour-Square Foot (BTU/(hr·ft²))
An imperial heat-flux unit (≈ 3.1546 W/m² per NIST SP 811) used universally in US HVAC engineering, building-envelope thermal analysis, and shell-and-tube heat-exchanger design per TEMA standards. ASHRAE design cooling loads (per ASHRAE 90.1 / 62.1), solar heat-gain coefficient (SHGC) tables for fenestration per NFRC 100/200, and US HVAC equipment-output ratings all use BTU/(hr·ft²). Reference values from ASHRAE Handbook: peak summer solar heat gain through a south-facing window in Phoenix ~200-300 BTU/(hr·ft²) at solar noon; design cooling load for a US suburban home 30-50 BTU/(hr·ft²) of conditioned floor area; commercial-building design heating load 20-30 BTU/(hr·ft²) (mixed-humid climate per ASHRAE 90.1). US shell-and-tube heat-exchanger thermal-design specifications per TEMA Standards routinely quote heat-flux design points in BTU/(hr·ft²) — typical ranges 50-500 BTU/(hr·ft²) for liquid-to-liquid service; 1,000-10,000 BTU/(hr·ft²) for boilers and condensers; up to 100,000 BTU/(hr·ft²) for once-through-steam-generator superheater sections.
Quick Facts
- 1 Watt per Square Meter equals 0.316998 BTU per Hour-Square Foot
- 1 BTU per Hour-Square Foot equals 3.15459 Watts per Square Meter
- Watt per Square Meter is a unit of heat flux
- BTU per Hour-Square Foot is a unit of heat flux
- This conversion is commonly used in fire protection engineering, electronics cooling, and solar energy
- The Watt per Square Meter belongs to the metric system
- The BTU per Hour-Square Foot belongs to the imperial system
Common Watt per Square Meter to BTU per Hour-Square Foot Conversions
| Watts per Square Meter (W/m²) | BTU per Hour-Square Foot (BTU/(hr·ft²)) |
|---|---|
| 0.01 | 0.00316998 |
| 0.1 | 0.0316998 |
| 0.25 | 0.0792496 |
| 0.5 | 0.158499 |
| 1 | 0.316998 |
| 2 | 0.633997 |
| 3 | 0.950995 |
| 5 | 1.58499 |
| 10 | 3.16998 |
| 15 | 4.75498 |
| 20 | 6.33997 |
| 25 | 7.92496 |
| 50 | 15.8499 |
| 75 | 23.7749 |
| 100 | 31.6998 |
| 250 | 79.2496 |
| 500 | 158.499 |
| 1000 | 316.998 |
| 5000 | 1584.99 |
| 10000 | 3169.98 |
Understanding Watts per Square Meter
The Watt per Square Meter (symbol: W/m²) is a unit of heat flux. The SI unit of heat flux density (ISO 80000-5 §5-10) — the rate of heat-energy flow per unit area perpendicular to the flow direction. W/m² is the universal working unit in heat-transfer analysis (Fourier conduction q = −k·∇T, Newton's law of cooling q = h·ΔT, Stefan-Boltzmann radiation q = ε·σ·T⁴), solar-energy and atmospheric science, building-envelope thermal modeling, electronics cooling, and radiation intensity. Reference values: the solar constant at Earth's top of atmosphere is exactly 1,361 W/m² (the standard reference value defined by IAU 2015 Resolution B3 / SORCE TIM instrument data); a clear-sky noon at sea level ~1,000 W/m² (the standard test condition for photovoltaic module rating per IEC 61215); average daily Earth-surface insolation 150-250 W/m² (region-dependent); human body emits ~75-100 W/m² as black-body IR radiation at skin temperature; CMB cosmic microwave background ~3.13 × 10⁻⁶ W/m² at 2.725 K. Building-envelope U-factors (W/(m²·K)) multiplied by ΔT yield heat flux in W/m². Also the SI unit for irradiance, sound intensity (in acoustics), and Poynting-vector electromagnetic flux.
It belongs to the metric measurement system.
Watts per Square Meter are commonly used in fire protection engineering, electronics cooling, and solar energy.
Understanding BTU per Hour-Square Foot
The BTU per Hour-Square Foot (symbol: BTU/(hr·ft²)) is a unit of heat flux. An imperial heat-flux unit (≈ 3.1546 W/m² per NIST SP 811) used universally in US HVAC engineering, building-envelope thermal analysis, and shell-and-tube heat-exchanger design per TEMA standards. ASHRAE design cooling loads (per ASHRAE 90.1 / 62.1), solar heat-gain coefficient (SHGC) tables for fenestration per NFRC 100/200, and US HVAC equipment-output ratings all use BTU/(hr·ft²). Reference values from ASHRAE Handbook: peak summer solar heat gain through a south-facing window in Phoenix ~200-300 BTU/(hr·ft²) at solar noon; design cooling load for a US suburban home 30-50 BTU/(hr·ft²) of conditioned floor area; commercial-building design heating load 20-30 BTU/(hr·ft²) (mixed-humid climate per ASHRAE 90.1). US shell-and-tube heat-exchanger thermal-design specifications per TEMA Standards routinely quote heat-flux design points in BTU/(hr·ft²) — typical ranges 50-500 BTU/(hr·ft²) for liquid-to-liquid service; 1,000-10,000 BTU/(hr·ft²) for boilers and condensers; up to 100,000 BTU/(hr·ft²) for once-through-steam-generator superheater sections.
It belongs to the imperial measurement system.
BTU per Hour-Square Foot are commonly used in fire protection engineering, electronics cooling, and solar energy.
Why Convert Watts per Square Meter to BTU per Hour-Square Foot?
Converting between Watts per Square Meter and BTU per Hour-Square Foot is a frequent requirement for engineers, scientists, and students working with heat flux values. Different industries and regions favour different unit systems, so having a dependable conversion tool saves time and prevents errors in technical calculations. Whether you are verifying a specification sheet, cross-checking simulation results, or preparing a report for an international audience, accurate heat flux conversion is essential.
Frequently Asked Questions
How do I convert Watts per Square Meter to BTU per Hour-Square Foot?
The SI unit of heat flux density (ISO 80000-5 §5-10) — the rate of heat-energy flow per unit area perpendicular to the flow direction. To convert Watts per Square Meter to BTU per Hour-Square Foot, multiply by 0.316998. For example, 25 W/m² equals 7.92496 BTU/(hr·ft²).
How many BTU per Hour-Square Foot are in 1 Watt per Square Meter?
There are 0.316998 BTU per Hour-Square Foot in 1 Watt per Square Meter.
How many Watts per Square Meter are in 1 BTU per Hour-Square Foot?
There are 3.15459 Watts per Square Meter in 1 BTU per Hour-Square Foot.
What is the formula for Watt per Square Meter to BTU per Hour-Square Foot conversion?
The formula is: multiply by 0.316998. This means 1 W/m² = 0.316998 BTU/(hr·ft²).
Is a Watt per Square Meter bigger than a BTU per Hour-Square Foot?
Yes. One Watt per Square Meter is larger than one BTU per Hour-Square Foot because 1 W/m² equals 0.316998 BTU/(hr·ft²), which is less than 1.
When do you need to convert between Watts per Square Meter and BTU per Hour-Square Foot?
An imperial heat-flux unit (≈ 3. Watt per Square Meter and BTU per Hour-Square Foot are both heat flux units, so conversion comes up whenever one source of information uses one unit and another uses the other — a classic cross-reference challenge in engineering, trade, travel, and everyday life.