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Online Calculator: Heat Transfer

{CalQlata © 01/01/20}

This calculator applies to the transfer of heat through a material barrier.

This calculator applies to flat surfaces, such as walls.

Enter the thermal properties of the wall
hover over the input labels (properties) for their [metric] units (see help below for Imperial unit conversion).

Metric Units (Watts, metres and seconds):

Input Property: Input Data Output Property: Output Data
temperature variation (δṮ): heat transfer rate (q):
thermal conductivity (k): heat transfer coefficient (U):
wall thickness (th): thermal resistance (R):
barrier area (A): thermal conductance (C):


CalQlata's Heat Transfer calculator is accessible from anywhere in the website using the shortcut key; "Alt" + "h"
The "Reset" button clears all calculations on the page and reinstalls default values (this button may not respond in the FireFox browser).
Reset can also be achieved by pressing the "F5" key.
Hover your cursor over the symbols for an associated description.

Thermal conductivity is the ease with which a material will transmit electro-magnetic energy between its constituent atoms. The more crystaline the atomic structure the better the transmission rate. This is why metals tend to be better conductors than, say; polymers.

The above calculation shows the rate at which energy (Watts = Joules per second) is transferred for a given thermal conductivity (k) and temperature difference (δṮ). If the [heat] energy disparity across a barrier of low thermal conductivity, the transfer rate (q) will also be low.

The purpose of this calculator is to specify a material of given thermal conductivity in terms of; heat transfer rate (q), thermal resistance (R) and heat transfer coefficient (U) for alternative purposes; conduction or insulation.
Note: Whilst 'q' varies with temperature difference, 'R', 'C' & 'U' do not.


The hover-title units are provided for guidance only. You need not use them if you prefer not to.
You may use any units you wish, but you will get out what you put in, for example;
if the above input data is entered [as provided] in metric units, e.g.; Watts (W), metres (m) and Kelvin (K);
        k = W/m/K, q = W (J/s), U = W/m²/K, R = K/W, C = W/K
or if they are entered in Imperial units, e.g.; British thermal units (Btu), feet (ft) & Rankine (R);
        k = (Btu/s)/ft/R, q = Btu/s (hp), U = (Btu/s)/ft²/R, R = R/(Btu/s), C = (Btu/s)/R
to convert from W/m/K to Btu/s/ft/R; you multiply the metric value by 0.0001605

Downloadable Version

Full downloadable versions of this calculator is available from this website at; Thermins.

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