THE NUMBERS, EXPLAINED
How to use this calculator.
Interest is applied to each opening nonnegative balance, then contribution and spending occur. Negative balances earn no interest and represent a funding shortfall; no borrowing cost.
Start with your inputs
Enter opening reserve, contributions by period, planned works spending by period, interest per period (%). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Opening reserve | 1000 |
| Contributions by period | 200,200,200 |
| Planned works spending by period | 100,1500,100 |
| Interest per period (%) | 0 |
A worked example
With the example inputs above, closing fund by period is 1100, -200, -100. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Closing fund by period | 1100, -200, -100 |
| Largest projected shortfall | 200 |
How this is calculated
Closing fund by period
Roll forward opening balance, interest, contribution and planned works for every period.
Largest projected shortfall
Find the largest negative closing balance.
Symbols and units
- a
- Opening reserve
- b
- Contributions by period
- c
- Planned works spending by period
- d
- Interest per period (%)
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
Interest is applied to each opening nonnegative balance, then contribution and spending occur. Negative balances earn no interest and represent a funding shortfall; no borrowing cost.
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?
Closing fund by period; Largest projected shortfall. 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: Interest is applied to each opening nonnegative balance, then contribution and spending occur. Negative balances earn no interest and represent a funding shortfall; no borrowing cost.
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.
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