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Stair baluster spacing calculator
Plan vertical balusters for a stair rail with rise-and-run geometry instead of guesswork. Enter the stair run, stair rise, baluster size, and target maximum opening to get an exact along-rake layout, rail marks, and cut summary instantly in the browser.
Why stair sections are different
A stair rail does not behave like a flat deck panel. Once the rail is on an angle, the opening measured along the rake becomes larger than the opening limit most people start from.
This calculator uses the stair rise and run to convert your maximum opening target into an allowed along-rake gap, then picks the minimum baluster count that fits. That is the part that gets misjudged most often when people reuse flat-panel spacing by eye.
Good fit for
- Deck stair guards with vertical metal or wood balusters
- Porch stair rails where you want an exact mark list before drilling or welding
- Rebuilds where the post locations are fixed and the stair angle is already set