# What is the best way to perform advanced calculations with Gravity Form, please?

My clients is a transportation company.  He wants a form which will calculate a price and integrate with Stripe or Paypal to accept 10% of the amount as deposit

##### Post Metadata
- Posted at: over 6 years ago
- Author title: Owner, dosh.ie
- Net upvotes: 1


## Comments
### Comment 1

Then you will want to set the product amount to be set as the 10% and have the Stripe Add-On take the payment just for that. I would add a html field in your form to explain what's going on and if the price is different per customer, I'd use php to calculate what that 10% discount is and then pass to the form when you call it (in php). Unfortunately the html field cannot be pre-populated so usually I use JS to change the html field content for the user. If that content also needs to be changed on a user-by-user basis, have JS AJAX to get the new total Then concat that response into the html.

##### Comment Metadata
- Posted at: over 6 years ago




## Related Product
[Gravity Forms](https://www.g2.com/products/gravity-forms/reviews)

## Related Category
[Online Form Builder](https://www.g2.com/categories/online-form-builder)

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