So I've seen a number of tables estimating calories burned while cycling based on weight and speed... and run across estimates ranging from 30-50 calories per mile.

It seems like experience may be as good a guide for non-elite athletes as trying to be absolutely precise in estimating calories burned based on wind, grade of climb, etc... So here's my question:

Yesterday I rode 84 miles, my longest ride yet by about 50 miles . (The length happened partially by accident). I was riding by myself, and didn't know how my body would react to that distance, so I was assiduous about refueling (as a runner, I know what bonking feels like and I wouldn't want it to happen to me alone, 20 miles from home, on a bike, in 85 degree weather). I was riding at a pretty brisk pace for me (averaged 16.5 miles, which really means 18-19 much of the time, except for some of those long, shallow hills where I was struggling to hold 13 riding into a headwind). Over the course of five hours on the bike, I consumed a total of 750 calories -- a clif bar, a luna bar, two bottles of sports drink and a bottle of vitamin water -- based on your experience, does this sound like a vaguely appropriate amount? It felt ok -- no bonking, but didn't feel like I was stuffing myself either. However, I'm not in the habit of eating while exercising (I can't eat anything more substantial than gel within hours of running), and this sounds to me like a recipe for gaining weight -- that's like, half a day's calories for me off the bike (I'm ~120 lbs)... Thoughts? Advice for fueling during long (for me?) rides?