This is an efficient device for performing calculations involving quantities with known or estimated uncertainties. This is also popularly known as the error propagation or the uncertainty propagation. It facilitates the computation of uncertainties in one of the two ways:

- The most probable uncertainty, also known as the standard error (or uncorrelated uncertainty), that is used when errors are independent;
- The maximum uncertainty, also known as the maximum error (or correlated uncertainty), that is used when they are not.

This calculator mostly operates in what we know as the *postfix* mode. This implies that you first need to input your values for X and Y in the preliminary step. Then, you go on to choose what you want to do with them. Although this comes later in the section under *Operation*.

To proceed, you need to position the cursor on the blank under “X”. Then, click the mouse and insert a value.

Another option is that you press the TAB key until the cursor appears in the blank and then type the number. In case if an error is found, use normal text-editing procedures.

Subsequently, enter values for X and dX, and if possible, for Y and dY.

Finally, click on the button for the desired operation or function. The equation for the calculation appears in the output field and the values of Z and dZ appear in their respective fields.