Can i create a formula field to calculate the time in business hours between Case created date to now/Closed date?

I'm pretty sure this can't be done without code. There is no formula that accesses the business hours settings. Sorry!

You could try this answer which calculates the time difference https://stackoverflow.com/questions/11126378/salesforce-formula-calculate-business-hours-between-two-dates/11129346 but you would have to make assumptions about the business hours and the formula wouldn't mirror exactly to them. Hopefully close enough