Heat Transfer Coefficient & Convection Calculator

Convective Heat Transfer, Boundary Layers & Heat Transfer Coefficient Metrology

The Heat Transfer Coefficient (h, film coefficient) quantifies convective heat transfer between a solid surface and a moving fluid:

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• Universal Heat Transfer Coefficient Conversion Formulas (ISO Standards)**:

h_BTU/(h·ft^2·^) = h_W/(m^2·K)5.678263 = h_W/(m^2·K) × 0.176110

h_W/(m^2·K) = h_BTU/(h·ft^2·^) × 5.678263

1 kcal/(h·m^2·^) = 1.163 W/(m^2·K) | 1 cal/(s·cm^2·^) = 41,840 W/(m^2·K)

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• Newton's Law of Cooling & Convective Resistance Formulas**:

Q = h × A × (T_s - T_∞) (Watts, W)

R_conv = (1) / (h × A)

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• Standard Convective Fluid Regime Benchmarks**:

• Free Natural Convection (Air): 5 - 25 W/(m^2·K) 0.88 - 4.40 BTU/(h·ft^2·^)

• Forced Air Convection: 25 - 250 W/(m^2·K) 4.40 - 44.0 BTU/(h·ft^2·^)

• Forced Water Convection: 500 - 10,000 W/(m^2·K) 88 - 1,760 BTU/(h·ft^2·^)

• Boiling Water & Condensing Steam: 2,500 - 100,000 W/(m^2·K) 440 - 17,600 BTU/(h·ft^2·^)

How to Use This Calculator

Enter your Heat Transfer Coefficient (h / Film Coefficient) (e.g. 50 in h), From Heat Transfer Coefficient Unit — choose from Watts per Square Meter-Kelvin (W/(m²·K) - SI Base Unit), BTU per Hour-Square Foot-°F (BTU/(h·ft²·°F) - Imperial Standard), Kilocalories per Hour-m²-°C (kcal/(h·m²·°C)), To Heat Transfer Coefficient Unit — choose from BTU per Hour-Square Foot-°F (BTU/(h·ft²·°F)), Watts per Square Meter-Kelvin (W/(m²·K)), Kilocalories per Hour-m²-°C (kcal/(h·m²·°C)), Convective Surface Area (A in m²) (e.g. 0.50 in m²), Surface-to-Fluid ΔT (T_s - T_∞ in °C) (e.g. 40 in Δ°C), and Convection Fluid Regime Benchmark — choose from Custom Convection Regime, Forced Air Cooling (50.0 W/(m²·K)) → 8.81 BTU/(h·ft²·°F) | Q̇ = 1,000 W (0.5m² @ 40°C ΔT) | R = 0.040 K/W, Natural Free Convection Air (10.0 W/(m²·K)) → 1.76 BTU/(h·ft²·°F) | Q̇ = 200 W. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Newton's Law of Cooling: Q_dot = h A Delta_T (in Watts)

Convective Thermal Resistance: R_conv = 1 / (h * A) (in K/W)

Worked Example

A mechanical engineer designing a forced-air cooled electronics enclosure with h = 50 W/(m^2·K) and surface area 0.50 m^2 operating at a 40^ temperature difference above ambient calculates the convective cooling rate is exactly 1,000 Watts.

Understanding Your Result

Evaluate your result in the context of your specific use case and relevant industry standards or reference values. A single calculated result is a starting point — test two to three scenarios to understand how sensitive the outcome is to your key input assumptions. For high-stakes decisions, verify your result against a secondary source or subject-matter expert before acting.