THE NUMBERS, EXPLAINED
How to use this calculator.
Each card has a separate spend plan, already restricted to purchases before its expiry. No transfers between cards or future purchases are assumed.
Start with your inputs
Enter gift-card balances, eligible planned spend before each expiry. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Gift-card balances | 30,50 |
| Eligible planned spend before each expiry | 20,80 |
A worked example
With the example inputs above, usable value by card is 20, 50. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Usable value by card | 20, 50 |
| Stranded total balance | 10 |
| Total additional cash needed | 30 |
How this is calculated
Usable value by card
Take the smaller of each balance and eligible planned spend.
Stranded total balance
Sum card balances not covered by planned spend.
Total additional cash needed
Sum planned spend exceeding each corresponding balance.
Symbols and units
- a
- Gift-card balances
- b
- Eligible planned spend before each expiry
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
Each card has a separate spend plan, already restricted to purchases before its expiry. No transfers between cards or future purchases are assumed.
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?
Usable value by card; Stranded total balance; Total additional cash needed. 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: Each card has a separate spend plan, already restricted to purchases before its expiry. No transfers between cards or future purchases are assumed.
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 →