SQL 2014 Database Size

I am writing here to have expert opinion on the issue we are facing at the time of restore of DB on "test company" in the "C" Drive the database which allocates/occupies 130GB to 140GB space on the drive as we have completed only 1 year after system initialization.

We would like to know that how much space it would be taking in next 4 to 5 years if it continues taking 130GB to 140GB in only 1 year.

Actual Backup size of DB is right now 13.5GB in .BAK form.