vent sizing

Looking to get my ducks in a row. I have tried to read the archives, but still a little fuzzy on some things.
What would my vent size need to be for a commode, one lav, a clothes washer and sink/dishwasher
I was reading where it is 1/2 of your main line, so .. using a 3" would be 1.5.I planned on using a 2" thew the roof good or do I need bigger.
Planned on using my vent lint from the toilet and tying in everything
to that... Thanks Mike

vent

The size you need depends on your code. Some areas would require a 3" vent, others would need two 2" and one 1 1/2", others MIGHT get by with a single 2". I am not sure if anywhere would approve a single 1 1/2" if it were the only vent.