THE NUMBERS, EXPLAINED
How to use this calculator.
Steady-flow average with sequential rental and charge/clean time. It excludes peak protection and battery endurance validation.
Start with your inputs
Enter visitor arrivals per hour, visitors renting an audio guide (%), average rental duration (minutes), charge and clean turnaround (minutes), serviceable audio-guide devices. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Visitor arrivals per hour | 120 |
| Visitors renting an audio guide (%) | 25 |
| Average rental duration (minutes) | 60 |
| Charge and clean turnaround (minutes) | 20 |
| Serviceable audio-guide devices | 35 |
A worked example
With the example inputs above, mean devices in full circulation is 40. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Mean devices in full circulation | 40 |
| Whole-device fleet for mean demand | 40 |
| Additional devices for mean demand | 5 |
How this is calculated
Mean devices in full circulation
Multiply device arrival rate by rental plus turnaround duration.
Whole-device fleet for mean demand
Round mean circulation inventory upward.
Additional devices for mean demand
Subtract the serviceable fleet.
Symbols and units
- a
- Visitor arrivals per hour
- b
- Visitors renting an audio guide (%)
- c
- Average rental duration (minutes)
- d
- Charge and clean turnaround (minutes)
- e
- Serviceable audio-guide devices
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions and limits
Steady-flow average with sequential rental and charge/clean time. It excludes peak protection and battery endurance validation.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Mean devices in full circulation; Whole-device fleet for mean demand; Additional devices for mean demand. The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: Steady-flow average with sequential rental and charge/clean time. It excludes peak protection and battery endurance validation.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Further reading
MIT Operations Management: Queueing and Little’s Law ↗
Background reading; this does not imply endorsement or independent review of SumFizz.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →