What this calculator does
Baluster / spindle spacing works out even spindle count and gap for a stair or deck railing. 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
FormulaSpindles = ⌊rail length / (spindle width + max gap)⌋; actual gap = (length − spindles × width) / (spindles + 1)
The inputs explained
| Field | What to enter |
|---|---|
| Railing length (cm) | A number, measured in cm. Starts at 300. |
| Spindle width (cm) | A number, measured in cm. Starts at 4. |
| Maximum allowed gap (cm) | A number, measured in cm. Starts at 10. |
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 railing length
Every other input is held at the calculator’s starting values while railing length varies. Select any row to load that scenario into the calculator.