THE NUMBERS, EXPLAINED
How to use this calculator.
Every incoming request produces the same fan-out. Cache hits avoid a downstream call; retries multiply only uncached calls. The supplied mean attempts includes the first attempt. This is expected workload, not a dependency-graph simulation.
Start with your inputs
Enter incoming requests, downstream calls per request, downstream cache hit rate (%), mean attempts per uncached call. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Incoming requests | 1000 |
| Downstream calls per request | 4 |
| Downstream cache hit rate (%) | 25 |
| Mean attempts per uncached call | 1.2 |
A worked example
With the example inputs above, logical downstream calls is 4,000. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Logical downstream calls | 4,000 |
| Expected uncached calls | 3,000 |
| Expected actual attempts | 3,600 |
| Attempts per incoming request | 3.6 |
How this is calculated
Logical downstream calls
Incoming requests × calls per request.
Expected uncached calls
Logical calls × (1−cache hit percentage/100).
Expected actual attempts
Uncached calls × mean attempts.
Attempts per incoming request
Fan-out × uncached fraction × mean attempts; valid even when incoming volume is zero.
Symbols and units
- a
- Incoming requests
- b
- Downstream calls per request
- c
- Downstream cache hit rate (%)
- d
- Mean attempts per uncached call
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
Every incoming request produces the same fan-out. Cache hits avoid a downstream call; retries multiply only uncached calls. The supplied mean attempts includes the first attempt. This is expected workload, not a dependency-graph simulation.
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?
Logical downstream calls; Expected uncached calls; Expected actual attempts; Attempts per incoming request. 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: Every incoming request produces the same fan-out. Cache hits avoid a downstream call; retries multiply only uncached calls. The supplied mean attempts includes the first attempt. This is expected workload, not a dependency-graph simulation.
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
OpenStax: percentages and proportions ↗
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 →