The cloud billing export that goes to bigquery does not contain any forecast spend data. This data is present in cloud billing – but not available for export.

This leaves us with two options to retrieve this billing forecast data:

  1. Make API calls to the billing API to retrieve the forecast data
  2. Use linear regression outside of cloud billing to calculate billing forecast.

Here is a link to a sample looker query analyzing the spend trend (forecast) for a billing dataset.