Heat Transfer Calculator
Steady-state conduction through a wall, or convection off a surface, in watts.
What is Heat Transfer?
Heat moves by conduction through a solid, by convection from a surface to a fluid, and by radiation without a medium. The first two are what a basic calculation covers, and they are steady-state one-dimensional forms: how many watts cross a wall of a given thickness and conductivity, or leave a surface of a given area into air at a given temperature difference. Both are the same product of a coefficient, an area and a ΔT, which is why a single page with two modes is honest about them.
How it works
Conduction is k·A·ΔT ÷ d, with k the material's conductivity in W/m·K and d the wall thickness — insulation works by making k and d small and large respectively, in the denominator and numerator. Convection is h·A·ΔT, with h gathered from a table (5–10 for still air, 25 for moving air, in the hundreds for water). Each mode also reports the thermal resistance (K/W), the quantity that adds in series for a multi-layer wall.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.