Wet food amount per day

I want to start my cats on wet food maybe mix wet and dry. But I don't know how much per day. About my cats:
Poppy: Female, 5-6 months, spayed
Pippin: Male, 1 year 3 months. Not fixed
Merlin: Male, 8 months. Not fixed

Thre is no set amount of cans of food a cat needs in a day. You just feed enough to keep the cat's tummy happy and the cat at an ideal body weight This can be several 3 oz cans daily or a little more than a 5.5 oz can daily. Every cat is different.

Some peple feed enough calories to maintain their cat's body weight. The general rule is to feed 20 to 25 calories per pound of ideal body weight daily. How much do each of your cats weigh? Is their weight ideal or do they need to gain or lose weight?

Calorie content isn't listed on most cans so use these charts:

http://www.petobesityprevention.org/wp-content/uploads/2010/05/Cat_Canned_Pouch_Foods.pdf

http://www.catinfo.org/docs/SortableCatFoodChartCatinfo.org2-22-13.htm

I suggest feeding each cat around 250 calories daily to start with. Spread the canned food out into two or more meals if you can. Or leave a little buit of dry food out for snacking on.  If the cats keep asking for more food, you can feed a little more calories. The kittens may likely  need a bit more food than the one year old.

Not related but why are the two males not fixed? If cost is an issue, you can look into low cost neuter clinics in your area.