THE NUMBERS, EXPLAINED
How to use this calculator.
Uses supplied walk times and origin weights; threshold is inclusive. No straight-line conversion, road-network routing or accessibility claim.
Start with your inputs
Enter supplied walk times from origins (min), population or demand at those origins, chosen catchment time (min). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Supplied walk times from origins (min) | 5,10,20 |
| Population or demand at those origins | 100,200,400 |
| Chosen catchment time (min) | 10 |
A worked example
With the example inputs above, origins inside catchment is 2. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Origins inside catchment | 2 |
| Demand inside catchment | 300 |
| Demand coverage (%) | 42.857143 |
How this is calculated
Origins inside catchment
Count origins with supplied time no greater than threshold.
Demand inside catchment
Add demand for origins inside the threshold.
Demand coverage (%)
Divide covered demand by all origin demand.
Symbols and units
- a
- Supplied walk times from origins (min)
- b
- Population or demand at those origins
- c
- Chosen catchment time (min)
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
Uses supplied walk times and origin weights; threshold is inclusive. No straight-line conversion, road-network routing or accessibility claim.
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?
Origins inside catchment; Demand inside catchment; Demand coverage (%). 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: Uses supplied walk times and origin weights; threshold is inclusive. No straight-line conversion, road-network routing or accessibility claim.
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: Solve proportions and their applications ↗
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 →