THE NUMBERS, EXPLAINED
How to use this calculator.
Constant consumption starts immediately. Units are divisible; expiry is a user-supplied usable window and not a food safety recommendation.
Start with your inputs
Enter pack quantity (units), usage per day (units/day), usable days before expiry, pack price. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Pack quantity (units) | 100 |
| Usage per day (units/day) | 2 |
| Usable days before expiry | 30 |
| Pack price | 20 |
A worked example
With the example inputs above, usable quantity is 60. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Usable quantity | 60 |
| Unused quantity | 40 |
| Price per used unit | 0.333333 |
How this is calculated
Usable quantity
Use no more than pack contents or demand before expiry.
Unused quantity
Subtract demand before expiry from pack contents.
Price per used unit
Divide pack cost by quantity actually used.
Symbols and units
- a
- Pack quantity (units)
- b
- Usage per day (units/day)
- c
- Usable days before expiry
- d
- Pack price
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
Constant consumption starts immediately. Units are divisible; expiry is a user-supplied usable window and not a food safety recommendation.
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 quantity; Unused quantity; Price per used unit. 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: Constant consumption starts immediately. Units are divisible; expiry is a user-supplied usable window and not a food safety recommendation.
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 →