GlenCalc

Baluster spacing calculator

Building codes require that a 4 in sphere can’t pass through a guard, so gaps must be under 4 in.

Your answer

Balusters13
Gap3.75 in

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How we worked it out

Updated as you change the numbers.

  1. Balusters n = smallest whole number with (span − n × width) ÷ (n + 1) ≤ the largest gap. Gap = (span − n × width) ÷ (n + 1).

Method and assumptions

The IRC (R312.1.3) requires guard openings that a 4 in sphere can’t pass through; using a target just under 4 in, such as 3 7/8 in, leaves a margin for wood movement.

Questions

How many balusters between posts 72 in apart?

13 balusters 1.5 in wide with gaps of about 3.75 in.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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