Thermal expansion calculators input any known constants and the user-provided values of variables into the expansion equation and output the delta, the change in size of the material. Thermal expansion is the natural phenomenon where materials expand and contract in response to the surrounding temperature. Different equations are necessary depending on whether the change in shape affects length, area or the volume of the object, and it is up to the user to choose the appropriate thermal expansion calculator.
The most commonly used calculator is for linear temperature expansion. Linear thermal expansion occurs when an object changes length and when this delta is proportionate to the temperature change. The calculator uses the equation D = L0*alpha*(t1-t2) where D is the change in length, L0 is the initial length, alpha is the expansion coefficient of the material, and t1 and t2 represent the change in temperature. In this case, all inputs are user-generated. The calculator takes the inputs, applies the correct mathematical operation from the equation, and outputs D, the change in the length.
Alpha, the expansion coefficient, is unique to the material, so you should look it up in an engineering table. Users sometimes mistake D, the change in length, for the final length of the material. To find the final length of the material, add(expand) or subtract (contract) the delta from the original length. Finally, it is important to ensure units are consistent and in the correct format whenever you are calculating a physics equation. Most thermal expansion calculators provide examples of what units are appropriate for each variable.