Stair rail spindle layout

Stair Baluster Spacing Calculator

Calculate stair baluster or spindle spacing from the stair rise and run instead of guessing along the rake rail. The result uses the sloped rail length, spindle width, maximum opening, and waste.

Units

Total stair rise (ft)Total stair run (ft)Spindle / baluster width (in)Maximum clear opening (in)Matching stair rail runs Waste / extras (%)Cost per spindle ($)

Spindles to buy

Equal opening

Rail angle / length

Rough cost

Stair guardrail code note

This is a spacing and material estimator. Check the stair guard height, handrail clearance, local 4 inch sphere rule, manufacturer instructions, and inspector requirements before cutting or installing.

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Baluster Calculator

Use a measured flat rail opening for deck or balcony baluster runs.

Baluster Spacing Code

Review the 4 inch sphere rule and stair guardrail spacing notes.

Stair Handrail Angle Calculator

Check stair rail angle and diagonal rail length from the same rise and run.

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Stair spindle spacing formula

Sloped rail length = sqrt(total rise² + total run²)

Spindles per run = ceil((sloped length - max opening) ÷ (spindle width + max opening))

Equal opening = (sloped length - spindles × spindle width) ÷ (spindles + 1)

Buy count = spindles per run × stair runs × (1 + waste %)

Sample takeoff

A stair with 3.5 ft rise, 5.5 ft run, 1.5 in spindles, and a 3.5 in maximum opening needs 15 spindles on the rail, or 17 to buy with 10% waste. The equal opening is about 3.48 in.A stair with 1.05 m rise, 1.65 m run, 38 mm spindles, and a 90 mm maximum opening needs 15 spindles on the rail, or 17 to buy with 10% waste. The equal opening is about 87 mm.

Stair Baluster Spacing Calculator FAQ

How do I calculate baluster spacing on stairs?+

Use the stair rise and run to find the sloped rail length, divide that length by spindle width plus the maximum allowed opening, then recompute the equal opening from the rounded spindle count.Use the stair rise and run to find the sloped rail length, divide that length by spindle width plus the maximum allowed opening, then recompute the equal opening from the rounded spindle count.

Should I measure along the sloped rail instead?+

If the rail is already installed, measuring the clear sloped distance between posts is best. Enter rise and run that match that same post-to-post stair section.If the rail is already installed, measuring the clear sloped distance between posts is best. Enter rise and run that match that same post-to-post stair section.

Is a 4 inch opening always code-safe?+

No. The 4 inch sphere rule is common for guards, but stair triangles, handrail clearance, local amendments, and product listings can be stricter. Treat this as a layout check, not code approval.No. The 4 inch sphere rule is common for guards, but stair triangles, handrail clearance, local amendments, and product listings can be stricter. Treat this as a layout check, not code approval.