FYI some tablets also can use as phone, e.g. huawei t3 or m3 lite. 8-inch or 10-inch form factor
finally the big phone we should get is 6 to 6.2 inch and it can put in your pocket comfortably
5" I already have problems putting in my pocket. So I use a 4.6" one. Seriously, so people carry a handbag around for this or what?