Operations
Margin per block hour is the ASC number that matters
By Better Software · Sun Sep 20 2026 · 9 min read
If you are deciding whether to keep or release an OR block, utilization by itself is the wrong number. The number that matters is contribution margin per block hour: net reimbursement minus variable direct cost, summed across the cases in that block, divided by the hours you allocated. That uses allocated hours, not just used minutes. A block can look “full” and still earn less than a block that looks half-empty.
That is why the usual debate between surgeons and administrators goes nowhere. One side points to a high utilization percentage. The other points to a busy schedule. Neither number tells you what the block actually contributes to the center’s distribution.
For an ASC owner, the practical question is not “What is block utilization?” It is “Which block should I release or reassign?” The answer is to rank blocks by dollars per allocated block hour, then use utilization only as a supporting signal.
Why utilization percentage does not answer the ownership question
Block utilization is a capacity measure. It tells you how much of the time you gave away was filled. It does not tell you whether the cases in that time were profitable enough to justify protecting the block.
LiveData’s perioperative guidance usefully distinguishes raw from adjusted utilization. Raw utilization is the simple share of block time filled. Adjusted utilization tries to account for release and release-back behavior so you can see how the block is actually used. That helps with scheduling, but it still stays inside the time dimension. It does not join time to dollars.
That matters because the denominator is the core problem. If you gave a surgeon 40 block hours and they used 30, the denominator for an ownership decision is still 40. The unfilled ten hours are not free. They are hours you could have given to someone else.
The specialty data show why the ranking can flip
HST’s 2024 State of the Industry data, summarized by Becker’s, show block utilization varying widely by specialty: GI at 59.6 percent, ophthalmology at 56.7, orthopedics at 35.1, and general surgery at 17.7. Those numbers are useful as a sanity check, but they are not a release policy.
They are also a good reminder that the most utilized block is not always the best-earning one. A specialty with lower utilization can still generate stronger contribution margin per block hour if its case mix has higher net reimbursement and lower variable direct cost. The reverse is also common. A high-utilization block can be packed with low-margin work, expensive implants, or heavy setup and sterile processing labor.
HST’s profitability guidance points in the same direction. It defines contribution margin per case as net revenue minus variable costs. Once you add specialized labor, turnover labor, implants, trays, and preference-card-driven supply cost, the arithmetic can change quickly. In other words, the block that looks strongest in the scheduler may be the weakest on the income statement.
The three data pulls you need
To calculate margin per block hour, you need three joins that most ASC stacks do not make for you.
1) Scheduler data
Pull the block owner, day of week, allocated minutes, actual room time or wheels-in/wheels-out, release timestamp, and any backfill flag. You need the allocated block hours because that is the capacity you committed, not just the hours eventually consumed.
2) Billing data
Pull net reimbursement per case, meaning actual collected revenue, not billed charges. Include payer, denial, and underpayment flags so you can spot where a block looks strong on paper but weak after collections.
3) Cost data
Pull preference card and implant or tray cost per case, sterile processing minutes, specialized setup labor, and turnover labor. If your cost system cannot identify these at the case level, you will understate the cost of high-complexity blocks, especially ortho and other implant-heavy specialties.
The join key is the real test. Ideally, you have one case ID that survives the scheduler, billing, and materials systems. If you do not, you need a controlled mapping table and a reconciliation process. Without that, the math will drift every time a case is moved, split, or rescheduled.
Choose the accounting rules before you compare blocks
Two centers can calculate the same block differently and still both be internally consistent. What matters is that you state the rules before you use the result to release a block.
| Allocation choice | Recommended treatment | Why it matters |
|---|---|---|
| Fixed overhead | Do not allocate it in the block score | You want contribution margin, not fully loaded profit. Fixed cost belongs in center-level reporting, not in the release decision. |
| Turnover labor | Include it when it changes with the block | Longer turnovers consume staffed time and reduce the value of the block. |
| Partially released block | Credit only the hours actually kept or backfilled, depending on the policy | Otherwise you may reward a surgeon for time the center recovered later. |
| Backfilled case | Decide whether the original owner keeps credit or whether credit follows the case | This is a policy choice. Pick one and apply it consistently. |
Sullivan Healthcare Consulting’s work on the cost of an empty OR is a useful reminder here. Their framing is about fully loaded OR cost and lost contribution, which is different from contribution margin per block hour. Use it to understand total economic drag, not to replace the block-level release metric.
A worked example that shows the inversion
Illustrative example only: one quarter, three surgeons, all numbers invented for explanation.
| Surgeon block | Allocated hours | Utilization | Net reimbursement | Variable direct cost | Contribution margin | Margin per block hour |
|---|---|---|---|---|---|---|
| GI | 100 | 60% | $210,000 | $96,000 | $114,000 | $1,140 |
| Ortho | 100 | 35% | $160,000 | $54,000 | $106,000 | $1,060 |
| General surgery | 100 | 70% | $145,000 | $52,000 | $93,000 | $930 |
In this example, the general surgery block has the best utilization and the worst margin per block hour. GI is in the middle on utilization but leads on dollars. Ortho has the lowest utilization, yet it nearly matches GI because the case mix is stronger than the raw percentage suggests.
That is the decision you want the report to make possible. If you rank only by utilization, you would release the wrong block.
Turn the number into a release policy
Once you have margin per block hour, define a release threshold in dollars, not percent. For example, you might say a block becomes eligible for release if its trailing three-month margin per allocated hour falls below a floor you set for the specialty or surgeon group.
The exact floor depends on your center’s economics. A center with scarce OR capacity may tolerate a lower floor than a center with excess supply. What should not vary is the unit of measure. If you want to protect earnings, the trigger has to be dollars per hour.
Many centers also use a 48- to 72-hour release window. That is mainly a fairness mechanism. It gives the original holder time to add cases or give the block back while still leaving time for someone else to use it. It is not an economic law. It is a scheduling rule that reduces hoarding and arguments.
That also explains why surgeons hoard block time. If the release process feels subjective, they protect time even when they are not using it. A transparent dollar threshold makes the tradeoff visible.
Build versus buy: what each system gives you, and what it does not
Most ASC software stacks already provide pieces of this answer. They just stop short of joining them.
| System type | What it usually covers | What is still missing |
|---|---|---|
| Scheduler and dashboard tools | Block ownership, utilization, release timing, case counts | Net reimbursement and case-level variable cost |
| Billing system | Collections, payer mix, denials, underpayments | Which block the case belonged to |
| Case costing / materials system | Implants, trays, supply cost, preference-card cost | Allocated block hours and release status |
| Reporting layer | Can combine the above if the IDs are stable | Only works if your case ID and block mapping are trustworthy |
HST Dashboards, SIS, Vizier, Copient, and similar products each cover part of the problem. The gap is the join. If your case ID survives across systems and your preference cards are reasonably accurate, a reporting layer may be enough. If you run multiple centers, have inconsistent case IDs, or rely on messy card data, you may need a custom data model before any dashboard will be believable.
That is why this is not really an analytics purchase. It is a data-integration problem with an ownership decision attached.
What the reader should ask Monday morning
Before the next board meeting, ask four questions:
- Do we have one case ID that links scheduler, billing, and cost data?
- Are we measuring net reimbursement, not charges?
- Are we including the variable costs that actually move with the block?
- Are we ranking blocks by dollars per allocated hour, not by utilization alone?
If the answer to any of those is no, the current utilization report is still useful, but it should not decide block release. It is a capacity report, not a management report.
FAQ
What is block utilization in the operating room and how does it relate to patient care?
Block utilization is the share of scheduled block time that is actually used. It helps you understand how well OR time is being filled, which can affect access, wait times, and scheduling efficiency. It does not by itself tell you whether the block is economically worthwhile.
How is block utilization calculated, and what is the difference between raw and adjusted?
Raw block utilization is usually used block time divided by allocated block time. Adjusted utilization adds rules for releases and backfills so the number reflects how the block behaved over time. Adjusted utilization is better for scheduling review, but it still does not measure margin.
What is a good block utilization benchmark, and why is the benchmark the wrong target?
Benchmarks vary by specialty and center size. HST’s 2024 data put GI at 59.6 percent and orthopedics at 35.1 percent, which already shows that one benchmark does not fit all. The better question is whether the block produces enough contribution margin per allocated hour to justify keeping it.
What is case costing in an ASC?
Case costing is the process of estimating the cost of a case by including items like implants, trays, supplies, and labor that vary with the case. It helps you see the true variable cost side of the margin equation.
Which procedures are most profitable in an ASC?
There is no universal answer. Profitability depends on payer mix, implant cost, staffing, turnover, and how well the center negotiates reimbursement. The procedures that look best in a national list may not be the most profitable in your block schedule.
If you want the right release decision, start with the number your scheduler and billing system each hold half of: contribution margin per block hour. Then decide which blocks deserve protection, which deserve reallocation, and which only look busy because nobody has joined the data.
For the same reason, this is the kind of problem where Better Software tends to be useful when the off-the-shelf reports stop short. The work is not buying another dashboard. It is joining scheduling, billing, and materials data that were never built to agree, then turning that into a policy an owner can defend. That is the same kind of multi-system healthcare engineering challenge we handle in other settings, including our healthcare work at /industries/healthcare.