Heat Transfer Calculator

Heat moves from warmer objects to cooler ones through three mechanisms: conduction, convection, and radiation. This calculator handles the two most common analytical cases, conduction through a solid wall or slab using Fourier's law, and convective heat exchange between a surface and a fluid using Newton's law of cooling. Knowing the rate of heat transfer in watts is essential for sizing insulation, selecting heating or cooling equipment, assessing energy loss through building elements, and designing heat exchangers. For conduction, Fourier's law says that heat flow equals the thermal conductivity of the material multiplied by the cross-sectional area and the temperature difference across the material, divided by its thickness. High conductivity materials like copper and steel pass heat quickly; low conductivity materials like glass wool and timber resist it. For convection, Newton's law of cooling replaces the conductivity and thickness terms with a single convective heat transfer coefficient, which combines the effects of fluid properties and flow conditions into one practical number. You select the mode you want, enter the relevant dimensions and material properties, and the calculator returns the heat transfer rate in watts and kilowatts, along with supporting values. Use the results as a starting point for sizing and design work rather than as a final engineering specification.

Results are theoretical; real-world values depend on surface finish, contact resistance, and fluid flow conditions. For engineering design, consult a qualified professional.