It is not always about the size but if it has 2 means of eggress (2 exits) and if it meets local codes for building. You should contact your local building department and ask for the requirements. Goo dluck with your renovation.
If you contact your local building inspector they should be able to tell you their requirements. Every city and town is different and may have different requirements. I have worked with my local building inspector before for some home improvement projects and I found them to be very helpful.