One of the extremely convenient (and very cool) features in RSForm Pro is the Calculations feature. The Calculations feature can be found by logging to the backend of the Joomla website, and then by going to RS Form Pro > Manage Forms, and then clicking on the form you wish to add the calculations to, and then clicking on the Properties tab on the top, and finally clicking on the Calculations tab at the bottom left.
Now, the obvious question would be, “what’s so cool about this feature?”
Well, let’s assume you have the following 3 fields on your form:
 Price
 Quantity
 Subtotal
Typically, you would like to have the Subtotal automatically calculated once the person enters/changes the Price and the Quantity. If you were to do this using pure JavaScript, it will take you a lot of time and you will have a lot of code to maintain. But, since you’re using RSForm Pro, you can do this instantly the following way:
 You go to the Calcuations page as described above.

You choose Subtotal from the dropdown.

You paste the following formula into the text field just left of Save this calculation:
Subtotal = {Price:value} * {Quantity:value}

You save the form by clicking on the Save button on the top left.

You check the form on your website and you watch the coolness in action!
The nice thing about this is that this feature can be used in complex calculations, and, more importantly, in derived calculations. By derived calculations we mean calculations using other calculations. For example, in the above form, you might have 3 subtotal fields: Subtotal A, Subtotal B, and Subtotal C, and each of these fields is the result of Price [n] x Quantity [n]. In this scenario, you may want a field called Total which is the sum of all the subtotals. You can easily do this using the Calculations feature by just assigning the following formula to the Total field:
{Subtotal A:value} + {Subtotal B:value} + {Subtotal C:value}
That’s it! Now when a person changes the price or the quantity of any product, the subtotals and the total will be automatically updated. This is also more convenient and much clearer than the following (longer) formula (which yields the same result):
({Price A:value} * {Quantity A:value}) + ({Price B:value} * {Quantity B:value}) + ({Price C:value} * {Quantity C:value})
But – nothing is perfect and every piece of software has bugs! In this case, the bug is evident when one of the fields is anything but a regular text or hidden field… Let’s say, for example, you have a dropdown field where the person chooses the quantity. In this case, the Subtotal calculation will not work, and consequently, the Total calculation will not work. Why?
Well, because when the field is a dropdown (also referred to as a select), a radio button group, or a checkbox group, the system assumes that the user can choose multiple values (of course, this is not possible in the case of a radio button group or a single select), and so it stores the value in an array, which then causes a problem when the system tries to use this value…
But, how to fix the problem?
There are several ways to fix the problem, and the easiest one, in our opinion, is to fix it in the script.js file, which is located under the components/com_rsform/assets/js folder. Here’s how you can fix the problem for the dropdown:
 Open the aforementioned file.

Search for the line:
values.push(element.options[o].value);

and add the following line before the above line:
return element.options[o].value;

Save the file, clear the cache, reload the page, and the problem should be solved!
You can apply the same fix for the radio buttons and the checkboxes! It is a very simple fix. The downside of this solution is that if you have a multiple select field that will be used for calculations in your form, then only the first value will be taken into consideration!
Now, if you, our very precious reader, are facing the same problem and if the above guide didn’t solve the problem (or if you feel that the whole thing is a bit complicated and you prefer that someone else does it for you), then please contact us, we will do it for you swiftly, professionally, and for a very affordable fee!