Help!? Options on how much wet cat food!?

So I have a 5 or 6 year old Russian Blue named Fox. He is about 14 pounds? Maybe 13, maybe 15. I'm feeding him Hills C/d diet wet cat food 5.5 oz after a bad urinary track infection and surgery where they created a vagina like pee hole. He's been doing better, but the food is so expensive. I'm thinking of switching to Purinas Pro Plan urinary health which is 3.0 oz. He's an indoor cat and not very active. Does anyone think I could switch from two 5.5 oz to two 3.0 oz a day?

Or any suggestions on other wet cat food to give him is much appreciated!

It isn't a one-size fits all kind of thing, but there is a calculator here for the general amount of calories a cat could be fed: http://petsci.co.uk/feline-calorie-calculator/

Looks like at 14lbs, a cat is recommended about 336 kcals. You could experiment within this range and see if your kitty needs more or less. One 6oz can of wet food can have anywhere from 100 to 200 kcals, it really depends on the brand and content. Brands like Weruva will generally have 100 - 130 kcals per 6oz can and Brands like Wellness and Instinct will have around 200 kcals. The number is usually on the can or usually on the manufacturer's website. Good luck!

I would not change the food without asking my vet. It sounds like your cat had some major urinary issues. It might be risky to change his food.

I have a cat that has urinary issues and Purina pro plan focus urinary health is the only one she eats. They make both dry and wet. Mine can only tolerate the wet unfortunately. She has not had any problems with it either. She usually eats 3 cans per day if that helps.

Angel had cystitis back in 2012 a couple of times. He was on the Purina UR SO Rx food for a little over a year to keep him crystal free. (he had sturvite crystals).

(the vet knew how I felt about all the bad ingredients in the Rx foods, so she compared the 3 urinary wet foods they had, & that one had the least, so we went with that.)  After about a year, I wanted to find something that would still address his urinary/pH issues, so he wouldn't have a recurrence, but be healthier ingredients, & a little less expensive. We have a great local natural pet food store here w/ very knowledgeable staff who showed me Dave's Restricted Diet pet food. I bought a couple of cans to try, angel loved it, so have been buying cases ever since!  (& other than it has some brown rice flour, it's also grain free!)

Here's where you can get it on line. OH, & my vet did a follow up ultrasound & urinalysis after he had been on it a couple of months, & all was clear!  

http://www.chewy.com/cat/daves-pet-food-restricted-diet/dp/101617

Dave's is a great small company. I emailed Dave to tell him our story, & thank him for making a better food available that met his special needs, & Dave himself emailed me back, & even asked if he could use my testimony on their site/soc. media! 

Hope that helps!    Oh yea, one more thing to add. I also still add a little water from the PUR filter to his food, just to stay on the safe side.