How can I tally the total quantity of products selected on my form?

I would like a field with the total quantity of items selected.

How can I do this please?

https://form.jotform.com/80166370645154

I have been checking your form and I can see you have currently a payment integration that automatically calculates the total on your form, you have also the total in a Form Calculation widget:

However, you may take a look on the following guides in order to perform calculations on your form: 

https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget

https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field

Here is a simple form that will show you how a value is passed over to the calculation widget: https://form.jotform.com/80165846658973 

I hope this helps. 

Thanks but you seem to have misread my question.

I do not need the total.

I need a field with the total quantity.

In the screenshot the answer would be 5

Apologies for the confusion and thank you for the details, so if you need to get the total quantities then it will not be possible while using the integration to sell products, you will need to switch to basic fields instead and perform the calculations following the guides I provided above. 

Here's an example: https://form.jotform.com/80165846658973 

Feel free to clone my form and see what I did there.

If you have questions, please let us know. 

 Thank you but I would like my list of products to be in a dropdown menu. is it possible to select quantity of items selected from a drop down menu?

That is also doable with dropdown menus. Continuing the test form my colleague showed you, here's a cloned version of it with dropdown menus this time.

https://www.jotform.com/80171706043953

I just picked the first 7 products on your form as an example to demonstrate how the idea will work.

The key features you need to make this work would be CALCULATION VALUES and the FORM CALCULATION WIDGET.

Related guides:

How-to-Assign-Calculation-Value

How-to-Perform-Form-Calculation-Using-a-Widget

I recommend you clone my form too so you can have a closer look on how it was setup.