THE NUMBERS, EXPLAINED
How to use this calculator.
For a retained disk the cutter centre travels outside the desired radius. For a hole it travels inside. This is geometric setup only: check pivot security, tool limits and a test cut separately.
Start with your inputs
Enter target circle diameter (mm), cutter diameter (mm), keep disk (1) or make hole (2). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Target circle diameter (mm) | 300 |
| Cutter diameter (mm) | 10 |
| Keep disk (1) or make hole (2) | 1 |
A worked example
With the example inputs above, pivot-to-cutter centre (mm) is 155. Change the inputs to explore your own scenario.
| Result | Example answer |
|---|---|
| Pivot-to-cutter centre (mm) | 155 |
How this is calculated
Pivot-to-cutter centre (mm)
Disk: (target diameter + cutter diameter) ÷ 2. Hole: (target diameter − cutter diameter) ÷ 2.
Symbols and units
- a
- Target circle diameter (mm)
- b
- Cutter diameter (mm)
- c
- Keep disk (1) or make hole (2)
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
For a retained disk the cutter centre travels outside the desired radius. For a hole it travels inside. This is geometric setup only: check pivot security, tool limits and a test cut separately.
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?
Pivot-to-cutter centre (mm). 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: For a retained disk the cutter centre travels outside the desired radius. For a hole it travels inside. This is geometric setup only: check pivot security, tool limits and a test cut separately.
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.
Read the quality report →