A urethra gauge for measuring an inner size of a urinary tract. The gauge permits a clinician to measure the size of the urethral lumen (proximal to an outer orifice of the urethra) before a catheterization is performed. Selecting a properly-sized catheter for insertion into a patient by measuring the size of the urethral lumen before performing a catheterization is believed to reduce: (1) catheter-associated-urinary-tract infections; (2) urethral injuries due to inserting a catheter that is too large for the urethra; and/or (3) leakage associated with catheters that are too small for a particular patient.