How much I eat and how much I burn vary tremendously from ride to ride.
If I ride at a conversational pace on flattish terrain on a cool day, I don't require much on rides up to 50 miles.
Throw in some hills, increase the temperatures, and ratchet up the pace and I'm decimating my stored sugar and I get dehydrated easily. I'll carry 5 servings of hammer gel and 48 oz of water with electrolyte tablets, and find some stops to refill water bottles and get some snacks. Out in the country I'm using a camelbak.
In the worst summer heat I will go through 48 oz of fluids and 2-3 gels on a 17-mile ride with a few short steep hills. Some of the fluids are consumed directly at the ride finish, and the ride starts 5 hours after lunch. I've done a rolling average 16-17 mph for that ride so I am out in the heat 90 minutes including the pre- and post- ride routines.