Length of stay (LOS) is a term to describe the duration of a single episode of hospitalization. Inpatient days are calculated by subtracting day of admission from day of discharge.
A common statistic associated with LOS is the average length of stay (ALOS), a mean calculated by dividing the sum of inpatient days by the number of patients admissions with the same diagnosis-related group classification. A variation in the calculation of ALOS can be to consider only length of stay during the period under analysis.
LOS is commonly used as a quality metric. Prospective payment systems for reimbursing hospital care promotes shorter LOS by paying the same amount for procedures, regardless of days spent in the hospital.