You might need one and a half times to twice your normal amount of calories, but it all depends on what your "normal" calorie load is based on normal activity. Also varies if you are more likely to be on the 65 mile side or the 115 mile side of the range. And flat ground is quite different from hills or mountains. Etc., etc., etc., etc.

I would do what Matchka says, go to the grocery store, look at how much you spend in a day for normal conditions.

Figure double that for the extra calories you will need.

Then add 50 percent on top of that since you will sometimes be shopping in higher priced stores like convenience stores instead of supermarkets.

If you go to a restaurant, assume it will cost 3 to 4 times as much as the food would have cost to just buy it and make it yourself - except beverages other than a glass of water are much more than 3 or 4 times as much.

On my last tour, we carried two days of freeze dried foods as an emergency supply in the bottom of our panniers, the emergency supply allowed us to relax and just keep pedaling until we found another store on our route. Never needed the freeze dried, but it made our life a lot easier when we did not have to obsess about where the next grocery store was when we were running low on food.