How do I create an app to calculate shipping costs

[JasonI_MRL]

Im currently trying to have my Shopify app calculate shipping costs (using address details from the checkout process in the store and calculated using a third party shipping calculator API). However im unsure on how to get my app to work/integrate with the custom shipping rates in the Shopify Admin. Is there any guides or ways to do this.

Below is a picture of my current options for the use of carriers. I do not wish to use Sendle as I want my own app to calculate the shipping costs.

Thanks in advance 🙂

[Anindita]

Hi @JasonI_MRL,

Which app you are using for calculating shipping costs? Ideally, if the app is installed and the zones are set then under the rate section (as you showed in the image) the drop-down will display the app.

[JasonI_MRL]

Hi @Anindita 

Thanks for the reply, Just to clarify, my current project involves me getting the calculated shipping costs from the app I'm developing (and that shipping costs is what my company provides as we are a logistics company). I'm looking for any documentation or references that can show me how to get my app to display the calculated shipping costs however I couldn't find any on Shopifys Dev Page. 

How would I enable my app to replace the shipping costs and rates in a storefront. Thank you.

[Côme]

Hi !

It's been a long time since you posted this, but I'm facing the same problem.
Have you been able to make your app appear in the dropdown ?
If so, how did you do it ?

Thanks !