Can I visually check brake pads for wear?

As I have no handbrake at all and the calipers wont adjust using the alen key I’m going to be swaping the calipers for refurbished units. Common sense tells me to replace the pads at the same time, but my wallet says - can I visually check the pads to see if they actually need replacing before I begin the job? I think I’m asking ‘how much pad should I be able to see whilst everything is still in place’? Dont worry I’ve enlisted help to change the calipers!

Happy New Year!

It’s only a 5 min job to remove a rear wheel to have a proper look. If a pad is less than 1.0 mm then it’s knackered. There is a grove in the centre of most pads, if that has gone then again the pad has had it’s day. Personally I would forgo the last few beers on NYE and fit new pads