How big do comets get? If my understanding is correct, Chury, the best explored comet so far is rather on the smallish side as comets go. Most comets observable with naked eye were so because they flew close to Earth, not because they were so big. I wonder, though, how big are the biggest ones. 

Let's get it in two variants:


How big is the biggest known comet? (mass, diameter)
Is there an estimate, or a theoretical limit on how big a comet can be? (for whatever reason, e.g. becoming a planet, breaking up due to tidal forces or whatever)
I suppose size limit of the comet is still under process but astronomers have found a few large ones though!
The comet Holmes which appeared in 2007 became brighter and also swelled up in size. Its nuclear size is only 3.6km (2.2 miles), but it released so much dust and gas so that it expanded to about 869,900 miles (1.4 million kilometers) i.e larger than the sun.
The largest comet in terms of nuclear size was discovered in the year 1729, comet Sarabat which had a nucleus of about $100 {\rm km}$.