casting flies

I was given a Redington Clearwater 7'6" 4wt fly rod and would like to know what is the smallest fly that can be cast with this rod

Thanks Skip for the reply

There is no lower limit on the size of the fly you can cast on a particular rod. From a casting perspective, consider a leader with no fly- it casts just fine. So I could take my 10 wt with a 7X tippet and cast a #32. The upper limit for rods/flies is another story for another thread.

The challenge comes in fishing with and catching fish on tiny flies I wouldn't want to use my 10 wt for fishing 20's let alone 32's. It is stiff as a poker in the tip and there would be no flex on a run. If that is actually the question you're asking, then it always will come down to how the rod flexes and how soft your wrists are, but yeah a soft-ish 4 wt should be able to go down to the tiniest flies with no problems.

thanks
rick

Thank you all very much for your replies this answers my question very well
cast_by_fly thanks for the explanation.