The occupancy rate is a calculation used to show the actual utilization of an inpatient health
facility for a given time period. It is expressed as a percent and other terms which are often used
synonymously include “percent occupancy,” “percentage of occupancy,” or “occupancy ratio.” In
the Bureau of Health Statistics, occupancy rates are routinely calculated for hospitals and nursing
homes and aggregated at the facility, county and state level. This information is very useful for
health planning purposes and is requested from the Bureau frequently.
To calculate the average occupancy rate for a typical one-year reporting period, two data item are
needed. These include “Inpatient Days of Care” and “Bed Days Available.” Definitions of these
two items are as follows:
INPATIENT DAYS OF CARE – Sum of each daily inpatient census for the year. To arrive at
this total, you would simply add together each daily census for the 365 days in the year. Other
synonymous terms include “total inpatient service days,” “occupied bed days,” or “census patient
days of care.”
BEDS DAYS AVAILABLE – The maximum number of inpatient days of care that would have
been provided if all beds were filled during the year. If 50 beds were available for use each day
during the year, bed days available would be 50 x 365 = 18,250. If the number of beds fluctuated
throughout the year, bed days available should reflect this and the calculation would be more
complicated. This will be discussed in more detail in the following paragraphs. Other terms used
for bed days available include “potential days,” “maximum patient days,” or “total inpatient bed
count days.”
To calculate occupancy rate, use inpatient days of care and bed days available in this formula:
(Inpatient Days of Care / Bed Days Available) x 100
The calculation of occupancy rates is not limited to the facility as a whole. Occupancy rates are
often calculated to determine the utilization of a specific inpatient unit such as obstetric,
psychiatric, medical/surgical, etc.
The occupancy rate is a valuable statistical measurement and is usually calculated for a certain
period of time (month, year, etc.) as opposed to calculating for one particular day. Determining
the occupancy for a longer time period reflects the degree to which hospital beds have been
utilized even though the number of beds may have changed during the reporting period. For the
purposes of this article, the time period for calculating occupancy rate will be a typical fiscal
year (July through June).
For the occupancy rate to be a true utilization indicator, bed days available must be calculated to
correctly reflect changes in the number of beds available for use during the year. If “bed days
available” are calculated incorrectly (for instance, the number of beds in service at the end of the
1
year are multiplied by the number of days in the year even though the number of beds in service
was considerably lower for several months), the resulting occupancy rate will be much lower
than actual. The following examples show how the result could differ if bed days available are
not calculated correctly:
A hospital had 300 beds in service from July 1 through February 28. The number of beds in
service then increased to 350 beds from March 1 through June 30. Bed days available should be
calculated as follows:
EXAMPLE 1 (Accurately reflects changes in bed capacity):
300 beds x 243 days = 72,900 (July 1 – February 28)
350 beds x 122 days = 42,700 (March 1 – June 30)
72,900 + 42,700 = 115,600 (Total Bed Days Available)
If bed days available were calculated based on the number of beds on the last day of the year
multiplied by the number of days in the year, the bed days available would be as follows:
EXAMPLE 2 (Does not reflect changes in beds during the year):
350 x 365 = 127,750
Following are occupancy rates based on the two different bed days available.
EXAMPLE 3 (Occupancy rate accurately reflects bed fluctuations):
(Inpatient Days of Care 98,560) / (Bed Days Available 115,600) = .853 x 100 = 85.3%
EXAMPLE 4 (Occupancy rate does not reflect lower number of beds available for use during
the first eight months of the fiscal year):
(Inpatient Days of Care 98,560) / (Bed Days Available 127,750) = .772 x 100 = 77.2%
The occupancy rate in Example 4 is much lower and not truly representative of bed utilization
during the year since the bed days available are calculated on 350 beds. The bed days available
(127,750) are inflated since the calculation (Example 2) assumes that all 350 beds were available
for use each day during the year. The inflated bed days available figure results in a lower
percentage of occupancy. Although it is simpler to calculate the bed days available using number
of beds in service on the last day of the year multiplied by the number of days in the year, this is
only accurate if there were no changes in the number of beds available for use.
