Help Estimating Calories?

Hi everyone!  I'm fairly new here, but I'm trying to get off to a good start with better eating habits and more exercise.

My coworkers took me to a restaurant today where I had a grilled caprese melt sandwich, and I'm really unsure how to estimate the calories.  I'd really appreciate hearing what you guys think.

The menu says "vine-ripened tomatoes, fresh mozzarella, basil aioli, on crusty ciabatta".

I ate it open faced, and both halves were probably about 5 inches long, with two pieces of buffalo mozzarella and 1.5 large tomato slices.

Thanks so much for your help!