My right calf is suddenly a little bigger than my left, i measured and it's about an inch bigger - no pain or other symptoms. what could it be?

Need to examine: It is not feasible to provide a meaningful opinion without examining you and your symptoms warrant evaluation by a physician.

Calf: Could be vascular such as dvt but usually there is discomfort However would start evaluation with a venous Doppler sonogram

Multiple measures.: Before becoming too alarmed, I would do a series of measurements at various times of the day, (Early morning, Noon and Evening), just to see if the enlargement is reflective of muscle activity or dependency.