Factors Affecting the Size of a Surgery Suite

The hospital surgery suite has undergone revolutionary change over the past several decades. For a long time, the focus has been on shifting surgery to a lower-cost outpatient setting. This has been replaced with a focus on lowering both the costs and risks of surgery with the ongoing migration from invasive to less-invasive surgery or noninvasive procedures. Minimally-invasive, image-guided, robotic, and telesurgery ― along with intraoperative imaging techniques ― continue to replace traditional surgical procedures. Aside from the economies of scale achieved with larger surgical suites, the biggest single factor contributing to the overall footprint of the surgery suite is the size and specialization of the individual operating rooms (ORs). Other factors include the proportion of outpatient surgery performed in the suite, and the type of patient care spaces provided, as well as the efficiency of the surgical suite layout.


In the traditional surgery suite, general operating rooms were used for a wide range of procedures and operating room specialization was limited to cardiac surgery and orthopedics. Cardiac surgery requires additional space for the perfusion team and equipment while orthopedic surgery requires significantly more equipment than most other surgical procedures. Real-time imaging has been a standard part of the operating room for many years — using mobile ultrasound or endoscopy units or c-arms (their name derived from their shape) along with the associated technologists. Although the definition can vary, the “hybrid operating room” is a revolutionary alternative to the conventional operating room and presents a unique planning challenge. The hybrid operating room has permanently installed equipment such as intraoperative computed tomography (CT), magnetic resonance imaging (MRI), and fixed c-arms ― typically used in conjunction with cardiovascular, thoracic, neurosurgery, spinal, and orthopedic procedures. These high-tech rooms enable diagnostic imaging before, during, and after the surgical procedure. This allows the surgeon to assess the effectiveness of the surgery ― and perform further resections or additional interventions ― all in a single encounter.


Surgery suites are designed with designated zones — unrestricted, semi-restricted, or restricted — that define the physical activities performed in each area. The space can be divided into six major areas as follows:

  • Patient intake area includes the reception/registration function, visitor waiting, and related support services and amenities. These spaces are usually located off a primary public corridor and separate from the patient treatment area. Patient intake space is generally proportionate to the number of ORs with minor economies of scale for larger surgery suites.
  • Post-anesthesia care unit (PACU) — also referred to as Phase I recovery — is where the patient is taken immediately post-surgery. After the patient recovers from a semiconscious state to being awake and alert, he/she is ready to be moved to the Phase II recovery area prior to discharge home (outpatient) or to a nursing unit (inpatient) for an overnight or multi-day stay. This space is generally proportionate to the number of ORs — with a ratio of one patient bay per OR.
  • Preoperative care/Phase II recovery area includes the pre-surgery preparation and holding area, the post-anesthesia (Phase II) recovery area, and associated support space. If separate areas are provided for pre-surgery patient preparation and post-anesthesia recovery, each area requires one patient bay per OR. However, these areas are commonly co-located to provide efficient staffing and flexible space utilization throughout the day as peak demand shifts from the morning (as patients are prepped) to later in the day (when the majority of patients are recovering). When combined, the total number of pre-surgery prep and Phase II recovery spaces can be reduced to a minimum of one space per OR. However, the eventual size of this area will be a function of the daily number of outpatients, their recovery time, the hours per day the area is staffed, and the type and size of the patient accommodations as well as the flexibility of the design.
  • Operating room space includes all invasive surgical operating rooms that require a sterile environment — general, specialty, and hybrid operating rooms — along with scrub stations and associated control rooms and space for ancillary equipment components. The ORs must be located in the restricted zone within the semi-restricted zone.
  • Operating room support space includes the central control station, clean core, supply/equipment storage, anesthesia workroom, and other support areas that are generally located proximate to the operating rooms in semi-restricted zone. Operating room support space is generally proportionate to the number of ORs.
  • Staff/administrative space includes administrative offices, staff lounges/lockers, and other staff amenities which are typically located in unrestricted space. Although there are economies of scale with larger surgical suites, larger suites typically have more specialty programs which, in turn, require additional staff. Some staff/administrative spaces may also be shared with other clinical functions and/or even located on a different floor level.

The patient intake area, preoperative care/Phase II recovery area, and staff/administrative space can be located in unrestricted space.


The figure below compares the department gross square feet (DGSF) per OR for medium and large surgical suites — with outpatients representing 60 to 65 percent of the cases — to a smaller ambulatory surgery suite with general operating rooms. DGSF represents the “footprint” of the surgical suite and includes the assignable net square feet (NSF) of all individual rooms, the width of the walls and partitions, and internal circulation corridors.

Surgery Space Allocation Bar Chart
Comparison of Department Gross Square Feet per Operating Room by Type of Space

A surgical suite with eight to twelve ORs will require between 2,700 and 3,500 DGSF per OR depending on the size and specialization of the ORs. The space required for a larger surgical suite may range between 2,400 and 3,200 DGSF per OR because of economies of scale. However, most larger surgical suites include a wide range of surgical specialties and perform complicated procedures that require more than a general operating room. On the other hand, ambulatory surgery suites may more commonly use general ORs. However, they require proportionately more space for pre-operative preparation and Phase II recovery. Once the number of ORs has been determined, the related post Estimating Surgery Space Based on the Number of Operating Rooms provides more rules-of-thumb.


Today, 400 NSF (37.2 NSM) is considered the minimum size for a general operating room. The minimum size of an operating room is determined by the size of the sterile operating field (relative to the size of the operating table, gurney, or procedure chair), the size of the anesthesia work zone, and the space required for movable equipment and circulation within the OR.

It should be noted, that for outpatient surgery facilities, The FGI Guidelines allows a clear floor area of 270 NSF (25.1 NSM) for an operating room that provides general anesthesia which can be further reduced to 255 NSF (23.7 NSM) for operating rooms where no general anesthesia is administered.

The FGI Guidelines recommends that operating rooms for image-guided surgery, or surgical procedures that require additional personnel and/or large equipment, be at least 600 NSF (55.7 NSM). However, where renovation work is undertaken, a clear floor area of 500 NSF (46.5 NSM) is allowed with a minimum clear dimension of 20 feet (6.10 meters). In addition to the incremental space for the larger ORs, additional storage space is required for related supplies and the specialty equipment when it is not in use. A hybrid operating room may require more than 600 NSF depending on the imaging equipment it contains. For example, in some hybrid operating rooms, the imaging equipment is designed to slide into and out of the surgical field to optimize the clear floor area when the equipment is not in use. As another option, a hybrid operating room may be designed with two surgical fields — one adjacent to the fixed imaging equipment and the other outside this area. The footprint of a hybrid operating room becomes even larger with the addition of a control room and equipment component room — for transformers, power distribution equipment, computers, and associated electronics.

For example, a surgical suite with all specialty operating rooms would require an additional 500 DGSF per OR compared to a suite with general operating rooms. Hybrid operating rooms require contiguous control rooms (minimum of 120 NSF) and equipment component rooms (typically 100 NSF) as well as additional space to store related supplies and other equipment when not in use. With a hybrid OR, an additional 800 DGSF per OR is required compared to a general OR — accounting for the incremental room size, control and equipment rooms, and additional equipment and supply storage.


Another factor that contributes to the overall DGSF per OR is the proportion of outpatients and the type of patient care spaces in the prep and Phase II recovery areas. A higher percentage of outpatients treated in the surgical suite increases the number of prep and Phase II recovery spaces which, in turn, increases the overall DGSF per operating room. The use of larger private rooms for outpatient Phase II recovery and/or pre-surgery preparation also requires more space. An ambulatory surgery suite with private rooms for prep and Phase II recovery may require up to 400 DGSF more per OR than a surgical suite that serves inpatients primarily using semi-enclosed bays.


The design of a surgical suite requires the use of a large net-to-gross space conversion factor — to account for circulation between unrestricted, semi-restricted, and restricted areas and the need for wider corridors to accommodate stretcher traffic — which further compounds incremental space increases for individual rooms. The net-to-department gross space conversion factor for the surgical suite generally ranges between 1.55 and 1.60 but may be as high as 1.80 depending on the design. Use of a single-loaded corridor results in less overall space for circulation while designs with “pods” of ORs and/or a perimeter corridor result in a higher net-to-gross conversion factor. The efficiency of the design can impact the overall size of the surgical suite by 10 to 15 percent.

Note: Step-by-step instructions for determining the size of the surgery suite can be found in the SpaceMed Guide.