Signature
TI = (n * B_bar - U) / D
| Inputs | Definition | Unit |
|---|---|---|
n | Number of days in the period | days |
B_bar | Average daily number of available beds over the period | beds |
U | Occupied bed-days in the period on the beds counted in B_bar | bed-days |
D | Discharges in the period, including deaths | count, above zero |
TI | Average number of days an available bed stands empty between successive patients | days |
|---|
Function
Bed turnover rate and turnover interval function
Maps the discharges, available beds and occupied bed-days of a period to the two measures reported as bed turnover: the turnover rate, the number of patients each bed served, and the turnover interval, the average time a bed stands empty between one patient and the next. It also expresses both through bed occupancy and average length of stay, and spreads the annual cost of a staffed bed over the patients it served. The records follow the notation of the Bed Turnover article. The throughput identity linking annual discharges to beds, occupancy and average length of stay is held on the Average Length of Stay page (HE-FM-ALOS-002) and is referenced here, not repeated.
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Implementations
Excel
Bed turnover interval from bed-days in one cell
Excel subtracts the named occupied bed-days cell from days in the period times average available beds, and divides by the named discharges cell.
=(DaysInPeriod*AvgAvailableBeds-OccupiedBedDays)/Discharges
Assumptions
Occupied and available bed-days from the same beds
U counts only days on beds included in B_bar. Patients in escalation beds that are not recorded as available add to U but not to available bed-days, and can make the interval negative.
Bed turnover interval as an average over the bed stock
TI is a mean over the whole period and bed stock. Empty time may be concentrated in some wards or seasons, so a short average interval does not show whether spare beds exist when demand peaks.
Worked examples
Bed turnover interval at the illustrative baseline
The baseline hospital has 146,000 available bed-days, 400 beds over 365 days, and 124,100 occupied bed-days. The 21,900 empty bed-days shared among 24,820 discharges give about 0.88 days each.
n = 365; B_bar = 400; U = 124100; D = 24820; TI = 0.8824
Bed turnover interval in route B before beds close
In route B, occupied bed-days fall to 105,485 with discharges unchanged, so empty bed-days rise to 40,515 and the turnover interval to about 1.63 days.
n = 365; B_bar = 400; U = 105485; D = 24820; TI = 1.6324
Common errors
Dividing empty bed-days by beds instead of discharges
Dividing the baseline's 21,900 empty bed-days by 400 beds gives 54.75 days, the empty days per bed over the year, not the gap between patients. The turnover interval divides by discharges and is about 0.88 days.
Sources
NHS Wales bed turnover interval indicator IP04
NHS Wales Data Dictionary. Indicator IP04 Bed turnover interval. Accessed 1 October 2026. Calculation: average number of unoccupied beds multiplied by the number of days in the period, divided by deaths and discharges during the period.
Canonical Identity
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