Length of stay
Length of stay (LOS) is the time a patient spends in the hospital for one admission. Inpatient days are counted from the day of admission to the day of discharge.
The average length of stay (ALOS) is found by adding up all inpatient days and dividing by the number of admissions for the same condition or group. Sometimes ALOS is calculated only for the period being studied.
LOS is usually skewed, meaning a few long stays pull the average up. Because of that, the median is often a better sign of a typical stay. Researchers try to predict or model LOS to see which factors affect how long a patient stays. Regression methods are common, and some studies suggest negative binomial regression as a good option.
LOS is used as a quality metric in health care. In some payment systems, hospitals are paid the same amount regardless of days spent in the hospital, which can encourage shorter stays. LOS also relates to other quality factors like patient satisfaction, fewer readmissions, and sometimes mortality. Discharge planning can help reduce LOS, especially for older patients, while still keeping satisfaction high and reducing readmissions within a few months.
A caution: focusing too much on LOS as a target can distort care, a idea known as Goodhart’s Law.
ALOS isn’t just for health care. It’s also used in events and venues to estimate how long attendees stay, which helps plan staffing, cleaning, parking, and food and beverages.
This page was last edited on 3 February 2026, at 11:29 (CET).