With the understanding that there's plenty of fudge room at either end, here's a chart matching tire and rim widths. There are advocates for going to the extremes, both wide and narrow, but the mainstream is near the center. Use it as a guide, then pick tire width according to your weight and road conditions. (fatter/bumpier go wider).



If you want to know more, there's plenty of info in the net. Search "bicycle tire and rim width".