We quantified gallbladder volume in 30 clinically healthy, fasted, cats, using an ellipsoid formula. All cats had a complete blood count and serum chemistry profile performed. Fasting times before sonography ranged from 12 to 16 h. The median gallbladder volume was 2.42 ml, with a range of 0.84-4.50 ml. The mean gallbladder volume was 2.41 ml. This reference range will assist clinicians when evaluating cats with hepatobiliary disease or suspected extrahepatic biliary obstruction.