Right now I am running 46/16 and want to gear a little lower. If I were to change the back cog out to an 18 or even bigger, how much adjustment to the chain will be required?

If I were to switch my chain ring out for a smaller one, lets say 44, then bump the cog up to 18, how much chain adjustment would be needed? Are we talking removing links or just moving the rear wheel hub back some to ensure chain tension?

Thanks for the info.