Too Snug or Too Loose? The size of your finger is determined by the distance around (⟳) your finger and is the same size no matter which jeweler measures it. Find your size at home! Check the time! Your ring size may fluctuate by as much as a quarter to half a size during the course of the day from natural swelling with heat or by seasonal temperature swings. Err on a quarter size larger to avoid discomfort.