Hemantgiri Goswami takes a look at auto-growth:
Auto Growth is a feature that allows database files (primary, secondary, and log) to expand when the database file becomes full – without manual intervention.
Auto Growth feature is handy when we do not want to increase the size of database files manually. There are two ways you can set auto growth – using SQL Server Management Studio (SSMS hereafter) and T-SQL. Auto Growth can be configured – In Percent and Megabytes.
Auto-growth isn’t a problem on its own, though growth sizes, especially in older versions of SQL Server, were far too low for medium- and large-sized databases.
I don’t particularly like the 2.5 MB example Hemantgiri shows. I have a quick rule of thumb which is 64MB for small databases, 256-512 for medium-sized databases, and 1GB for large databases (assuming my underlying disk is fast). This limits the number of auto-growth events and, for log files in particular, keeps virtual log file counts more reasonable.