THE NUMBERS, EXPLAINED
How to use this calculator.
Compare equivalent sanding tasks using your measured service life. Lists match in order. Cost per hour ignores machine energy and labour. Ties choose the first pack; a cheaper hour is not a claim about finish quality.
Start with your inputs
Enter pack prices (£), discs in each pack, measured minutes of use per disc. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Pack prices (£) | 12,20 |
| Discs in each pack | 10,20 |
| Measured minutes of use per disc | 30,20 |
A worked example
With the example inputs above, cost per disc (£), in pack order is 1.2, 1. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Cost per disc (£), in pack order | 1.2, 1 |
| Cost per hour (£), in pack order | 2.4, 3 |
| Lowest cost-per-hour pack number | 1 |
How this is calculated
Cost per disc (£), in pack order
For each pack, price divided by disc count. Listed values round to six decimal places.
Cost per hour (£), in pack order
For each pack, cost per disc × 60 ÷ measured minutes per disc.
Lowest cost-per-hour pack number
Choose the first pack with the smallest unrounded cost per hour.
Symbols and units
- a
- Pack prices (£)
- b
- Discs in each pack
- c
- Measured minutes of use per disc
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
Compare equivalent sanding tasks using your measured service life. Lists match in order. Cost per hour ignores machine energy and labour. Ties choose the first pack; a cheaper hour is not a claim about finish quality.
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?
Cost per disc (£), in pack order; Cost per hour (£), in pack order; Lowest cost-per-hour pack number. 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: Compare equivalent sanding tasks using your measured service life. Lists match in order. Cost per hour ignores machine energy and labour. Ties choose the first pack; a cheaper hour is not a claim about finish quality.
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: geometric formulas and arithmetic ↗
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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