Obviously the best thing is to throw a tape on there and see what the actual "usable" width is. Also, the size of the prospective recliner will be important as they come in all kinds of sizes.
When you ask "how big" I'm thinking you're just trying to find size vs a "big" recliner?? I bought 2 huge leather recliners for the house because I thought I liked them; sort of like sitting in/on your own personal love seat. Nice for a while but DW and I are both kind of wanting something smaller - so you can at least put your arms on the arms of the chairs;
don't try to big like that and get it through the door even with the back removed...