**Marina2525**Building first Ecommerce Form on JotForms. I originally put everything into the Inventory Widgets (Products and Max Quantities. ) Now, I am trying to add the Payment I set up. It is asking me to re-write each product, but has no way to count or add Max Quantities. Will it see my Inventory fields and be able to count down inventory, or do I need to add inventory after Im done wiht the Payment Wizard?

- JotForm Support
**Welvin**You have to calculate (calculation widget) the inventory widget in the form. See this sample equation in the calculation:

The left and right bracket mean to get the total price first of each inventory widget in the form.

Here's our guide on how to calculate: https://www.jotform.com/help/259-How-to-perform-calculation-in-the-form.

To pass the total amount to the Payment field, you need to configure the payment field to get the price from the calculation. Here's a guide: https://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field. You do not need to setup the product items again in the payment field configuration, just the total of the inventory widgets.

Let us know if you need further assistance.