Inputs
Formula used
availability_factor = (1 − downtime%) × (1 − buffer%)
available_hours = berths × period_hours × availability_factor
How to use this calculator
- Choose a method: measured totals for audits, or forecast for planning.
- Enter berths and the assessment period you want to study.
- Add planned downtime and a buffer that matches your risk level.
- Provide occupied hours, or enter calls and service-time details.
- Press Calculate to view occupancy and berth recommendations.
- Download CSV for spreadsheets, or PDF for sharing reports.
Occupancy as a planning KPI
Berth occupancy links traffic demand to quay capacity. It summarizes how intensively berth positions are used across a defined period, helping teams compare scenarios, justify upgrades, and set service targets. For marine construction, it also supports staging plans for barges, deliveries, and temporary moorings.
Defining usable berth-hours
The calculator converts your study period into hours, then reduces it with downtime and an operational buffer. Downtime represents planned unavailability like maintenance, dredging windows, or access restrictions. Buffer represents margin for weather, safety holds, tug delays, paperwork, and recovery after disruptions.
Measured versus forecast inputs
Use the measured method when logs already provide total occupied berth-hours. Use the forecast method when planning demand from vessel calls. Forecasting combines average berth time, changeover time, a peaking uplift for uneven arrivals, and an efficiency factor reflecting how smoothly operations run.
Interpreting bands and spare time
Spare/deficit hours show how far your plan sits from usable capacity. Positive spare time improves resilience; deficits often imply queues, overtime, or rejected arrivals. Sustained occupancy above about 75% typically increases congestion sensitivity when arrivals cluster or productivity varies.
Sensitivity checks and reporting
Run several buffers and peaking values to test robustness. A small uplift can change recommended berth count because the target cap is applied to usable hours. Example data: 4 berths, 30 days, 8% downtime, 10% buffer, and 2,100 occupied hours gives 2,980.8 available hours, 70.45% occupancy, and 880.8 spare hours. Another case: 6 berths over 90 days with 6% downtime and 12% buffer yields 11,428.2 available hours; if occupied hours rise to 6,200, occupancy is 54.26%.
- Audit month: occupied 2,100 h → occupancy 70.45% (4 berths).
- Peak quarter: occupied 6,200 h → occupancy 54.26% (6 berths).
- Access constraint: occupied 800 h → occupancy 116.69% (3 berths).
FAQs
What period should I use for occupancy checks?
Use a period that matches your decision. Monthly helps operations review; quarterly captures seasonality; annual supports budget planning. Keep the same period when comparing scenarios so occupancy and spare hours remain comparable.
How do downtime and buffer differ?
Downtime is planned unavailability, like maintenance closures and restricted access. Buffer is a management margin for uncertainty such as weather, variability in arrivals, safety holds, or delayed changeovers. Both reduce usable berth-hours.
Why can occupancy exceed 100%?
Occupancy can exceed 100% when occupied hours are greater than usable available hours after downtime and buffer. That indicates a deficit, likely causing queues, delays, overtime, or the need for more berths or longer operating windows.
When should I use the forecast method?
Use it for early planning when you have expected vessel calls and average service times, but not detailed logs. Add peaking and efficiency values to reflect real variability so the result is not overly optimistic.
What target occupancy should I aim for?
Many terminals manage to a cap around 60–75% for steady service, depending on variability and service priorities. Choose a cap that matches your reliability requirement, then review recommended berths and spare hours.
How is recommended berth count calculated?
The tool divides occupied hours by usable hours allowed at your target cap. Usable hours are based on berths, period hours, downtime, and buffer. It then rounds up to the next whole berth to meet the cap.
How do I share results with my team?
After running a scenario, download CSV for spreadsheets and trend tracking. Download PDF for quick approvals and meeting packs. Run multiple scenarios and keep the session history table as your comparison log.
Example data table
| Scenario | Berths | Days | Downtime% | Buffer% | Occupied hours | Available hours | Occupancy% |
|---|---|---|---|---|---|---|---|
| Measured month (maintenance week) | 4 | 30 | 8 | 10 | 2,100 | 2,980.8 | 70.45 |
| Forecast quarter (seasonal peak) | 6 | 90 | 6 | 12 | 6,200 | 11,428.2 | 54.26 |
| Stress test (limited access) | 3 | 14 | 20 | 15 | 800 | 685.4 | 116.69 |
Example values are illustrative for planning and review workflows.
Saved calculations (this session)
Tip: For design checks, test multiple buffers and peaking values to see sensitivity.