You said there were about 300 calories/can in another thread, right? One a day seems a little low for a dog his size, even for weight loss and low activity. This article seems like a good place to start: Basic Calorie Calculator | Veterinary Medical Center
If I'm reading the chart correctly (it sure is tiny), you're looking between 500 and 600 calories/day for weight loss. Every dog is different, of course, so you'll still need to monitor his weight and body condition to make sure he's losing weight at a healthy rate (not too fast) at that calorie level, and you may need to adjust again if he plateaus before hitting your weight goal for him, but if he were mine I'd start closer to 2 cans a day at 300 calories/can.
If I'm reading the chart correctly (it sure is tiny), you're looking between 500 and 600 calories/day for weight loss. Every dog is different, of course, so you'll still need to monitor his weight and body condition to make sure he's losing weight at a healthy rate (not too fast) at that calorie level, and you may need to adjust again if he plateaus before hitting your weight goal for him, but if he were mine I'd start closer to 2 cans a day at 300 calories/can.