Inpatient Days Calculator - Calculator Academy

Enter the admission date and discharge date into the calculator to determine the number of inpatient days.

Note: This calculator uses the selected counting convention (excluding discharge by default). Hospitals/insurers may define and bill inpatient days differently—confirm your facility’s policy for official reporting.

Related Calculators

Inpatient Days Formula

The following formula is used to calculate the number of inpatient days for a given admission and discharge date (as a date difference, i.e., counting midnights and excluding the discharge date).

D = (D_d - D_a)

Variables:

D is the number of inpatient days
D_d is the discharge date
D_a is the admission date

To calculate the number of inpatient days, subtract the admission date from the discharge date (this gives the number of midnights between the two dates; some policies instead count calendar days and may add 1).

What is an Inpatient Day?

An inpatient day refers to a 24-hour period during which a patient stays in a hospital or healthcare facility for treatment. The count of inpatient days is used to measure the length of stay for a patient, which can be important for medical billing, resource allocation, and evaluating the efficiency of healthcare services. Inpatient days may be counted as the number of midnights between admission and discharge, or as calendar days including discharge, depending on the facility/insurer policy.

How to Calculate Inpatient Days?

The following steps outline how to calculate the number of inpatient days.

First, determine the admission date (D_a).
Next, determine the discharge date (D_d).
Finally, calculate the number of inpatient days using the formula D = (D_d - D_a).
After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

Admission Date (D_a) = 2023-01-01

Discharge Date (D_d) = 2023-01-10

Result: 9 inpatient days when excluding the discharge date (counting midnights). If counting calendar days including the discharge date, the result is 10.