sienna to lake garda

It depends on where on lake Garda, but I would say from 3.5 to 4 hours.

I would like to go to Sirminone. but if it takes 4 hrs then i would want to spend a night at somewhere else in between.
where would you recommend?

Sirmione is probably 3.5 hours. It's on the southern shore therefore closer to where you are coming from. The drive is entirely on 4 to 8 lane freeways. I wouldn't consider 3.5 hours a long drive,, but if you want to stop along the way, the major cities you will be driving by are (in this order): Florence, Bologna, Modena, Mantua. Bologna and Modena are roughly half way.

wow. Thanks so much! do you recommend spending a night in bologna or go straight to Sirmione and spend a night there? also thinking of verona to spend a night....

should I stop by vernona first and go to sirmione ?
bologna 1night
verona 1 night
sirmione 1 night
then back to venice.

I would go straight without stopping in Bologna, except maybe a few hours to visit a bit of Bologna and eat lunch (best food is there). Certainly I wouldn't spend the night there. If Sirmione is your destination, you should spend your three nights there. You can visit Verona as a day trip from Sirmione, just 40 min drive or 20 min by train from nearby Peschiera (no train in Sirmione). I wouldn't change hotels so often, that's a time waster. Just use your hotel in Sirmione (or wherever you want on the lake) to visit both Verona and Lake Garda.

wow~ that is a lot of help! thank you so much!
I would definitely spend my nights in sirmione! very excited!
any recommendation for place to stay there?