About the Heat Transfer Calculator
What is the Heat Transfer Calculator?
Heat moves in three ways. This heat transfer calculator handles each: conduction through a solid (Fourier's law), convection from a surface to a fluid (Newton's law of cooling) and thermal radiation (Stefan–Boltzmann law).
Choose the mode and enter the area, temperatures and the property that matters for it.
How to use the Heat Transfer Calculator
- Mode (sample: Conduction through a wall)
- Area (m²) (sample: 10)
- Hot Side Temperature (°C) (sample: 40)
- Cold Side Temperature (°C) (sample: 26)
- Thermal Conductivity k (W/m·K, conduction) (sample: 0.81)
- Thickness (mm, conduction) (sample: 230)
- Heat Transfer Coefficient h (W/m²·K, convection) (sample: 10)
- Emissivity (radiation) (sample: 0.9)
- Press Calculate Heat Transfer (results also refresh as you type). The result card shows the Heat Flow, along with Heat flux, Energy per day, Temperature difference and Formula.
Formula used
Conduction Q = k A ΔT ÷ L; Convection Q = h A ΔT; Radiation Q = ε σ A (T₁⁴ − T₂⁴)
- σ = 5.67 × 10⁻⁸ W/m²·K⁴
- T = absolute temperature (K) for radiation
Real walls combine all three; use the thermal resistance calculator for layered walls.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Mode | Conduction through a wall |
| Area (m²) | 10 |
| Hot Side Temperature (°C) | 40 |
| Cold Side Temperature (°C) | 26 |
| Thermal Conductivity k (W/m·K, conduction) | 0.81 |
| Thickness (mm, conduction) | 230 |
| Heat Transfer Coefficient h (W/m²·K, convection) | 10 |
| Emissivity (radiation) | 0.9 |
| Result | Value |
|---|---|
| Heat Flow | 493.04 W |
| Heat flux | 49.3 W/m² |
| Energy per day | 11.83 kWh |
| Temperature difference | 14°C |
| Formula | Q = k × A × ΔT ÷ L |
Tips for using the Heat Transfer Calculator
- Natural convection in air has h of about 5–25 W/m²·K; forced air 25–250.
- Shiny foil (low emissivity) in roofs sharply cuts radiant heat gain.