Background Ammonia is produced and excreted by the kidney, contributing to systemic acid‐base homeostasis through the production of bicarbonate. Disorders of acid‐base balance can lead to many clinical problems and measuring ammonia excretion helps in determining if the kidneys are responding to acid‐base challenges appropriately. Reference intervals are integral to clinical decision‐making, and there is no current RI for the urine ammonia‐to‐creatinine ratio (UACR) in dogs. Objective This study aimed to generate an RI for the UACR in healthy adult dogs. Methods The study used adult, client‐owned dogs that were presented to the University of Florida Primary Care and Dentistry service (n = 60). Physical examinations were performed and serum chemistry and urinalysis samples were obtained. Urine ammonia and creatinine concentrations were determined. Dogs were excluded if there were significant abnormalities in either their urinalysis or serum chemistry results. The RI for the UACR was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology. Data were evaluated for correlation with serum bicarbonate, weight, age, and sex. Results The RIs for the UACR were 0.16‐23.69 with 90% confidence intervals for the lower and upper limits of (0.13‐1.17) and (20.50‐23.75), respectively. No significant impact of age, sex, or weight was found. There was no discernable relationship between serum bicarbonate and UACR. Conclusions Establishing an RI for UACR in healthy adult dogs will allow for further studies to determine if alterations are observed during specific disease states.