Trying to figure out amount to feed of wet/dry food in combination

I have two 15-month old cats, a boy and a girl (litter mates). We went to the vet today for their annual visit and boy weighs 10.7 lbs and is slightly underweight for his frame and girl weighs 10.2 and is slightly overweight for their frame. I'm trying to introduce a little dry food into their diet because my work schedule has changed and having that option would give me some flexibility, but I'd like to keep them primarily on a grain-free wet food. I have been googling and can't figure out how much I should be feeding them, and how dry food compares in quantity when pairing it with wet food (same day, not same meal)?

Anyone have any advice? 

Generally, the recommendation is to feed 20 calories per pound of bodyweight. As one is a little underweight and the other a little overweight, feed for their ideal weights rather than their current weights

It's impossible to give an estimated of how much food they should get (in terms of oz/can size etc) as calories can vary so much between brands. The ratio of wet to dry is easier, however. Let's say you wanted to feed half and half wet and dry. Simply work out what a full day's ration for both the wet and dry individually, then halve them both. The same applies for any other ratio (Hope that makes sense ). [article="31116"][/article]

Personally, I would stay with all wet.  A breakfast before work, an after work snack, and another meal before bed.  At 15 months your kitties could also do fine with 2 meals a day.  However...

If you have decided to add dry kibble, then look at how many calories per day your cats have been eating.  The information is on the can.  The kcals/cup will be listed on the dry food as well.  You might want to start with the same kcals per day as you have been feeding.  Just decide what percent of their calories you want to feed canned versus dry.

Having one overweight and one underweight cat at the same time (been there, done that) can be a challenge.  You may need to take your underweight boy to a separate room once a day for an extra bite or two of food.  The weight doesn't sound like a big problem right now with both cats being between 10-11 pounds, but it is something to keep a close eye on, especially with a diet change.  (Dry kibble is the a major contributor to fat old cats.)