What this calculator does
Bolt circle spacing works out straight-line spacing between adjacent bolt holes evenly spaced on a bolt circle. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaChord spacing between adjacent holes = 2 × radius × sin(π / number of holes)
The inputs explained
| Field | What to enter |
|---|---|
| Bolt circle diameter (mm) | A number, measured in mm. Starts at 150. |
| Number of holes | A number. Starts at 6. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with bolt circle diameter
Every other input is held at the calculator’s starting values while bolt circle diameter varies. Select any row to load that scenario into the calculator.
How the answer changes with bolt circle diameter