So you want to build a budget for your feature film.

and how.

This is what I would do,

read your script

• build a list of scenes, then of locations
• build a list of characters, then potential cast

a list of

• crew, for dev/pre/production/post
• props, including set deck
• equipment needs
• stunts, spfx
• plenty of lists

this is a framework for things that will need to be resourced.

Now, whats the budget - the budget is as much money as comes in for the project. 5k, 500k, 5mil.
We don't have to spend it all, but we can't spend more than it is.

So, you want to build a budget for your feature film?

 

Easy proposal: 5 to 15k for 1-2 months.

You don't build a budget in a day.
You could. It would just need weeks of revisions.
In which case it wasn't built in one day.