THE NUMBERS, EXPLAINED
How to use this calculator.
One reusable item lasts the supplied whole-use lifetime, then is replaced at the same price. Reports first-item break-even and recurring lifetime economics.
Start with your inputs
Enter reusable purchase price, disposable price per use, reusable cleaning cost per use, reusable lifetime (uses). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Reusable purchase price | 20 |
| Disposable price per use | 1 |
| Reusable cleaning cost per use | 0.2 |
| Reusable lifetime (uses) | 50 |
A worked example
With the example inputs above, first-item break-even uses is 25. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| First-item break-even uses | 25 |
| Reusable lifetime cost | 30 |
| Disposable cost over same uses | 50 |
| Break-even within first lifetime | Yes |
How this is calculated
First-item break-even uses
Divide purchase price by savings per use and round up.
Reusable lifetime cost
Add purchase and cleaning over the supplied life.
Disposable cost over same uses
Multiply disposable per-use price by reusable life.
Break-even within first lifetime
Compare break-even use count with supplied lifetime.
Symbols and units
- a
- Reusable purchase price
- b
- Disposable price per use
- c
- Reusable cleaning cost per use
- d
- Reusable lifetime (uses)
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
One reusable item lasts the supplied whole-use lifetime, then is replaced at the same price. Reports first-item break-even and recurring lifetime economics.
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?
First-item break-even uses; Reusable lifetime cost; Disposable cost over same uses; Break-even within first lifetime. 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: One reusable item lasts the supplied whole-use lifetime, then is replaced at the same price. Reports first-item break-even and recurring lifetime economics.
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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