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Spindle Spacing Calculator

Accurately calculate spindle spacing for stairs or decks with our free online Spindle Spacing Calculator. Easy, fast, and code-compliant results.

Whether you're building a deck, staircase, or railing, knowing the correct spindle spacing is crucial. Improper spacing can lead to safety violations or uneven aesthetics. That’s why we developed this easy-to-use Spindle Spacing Calculator — a smart, web-based tool that helps homeowners, carpenters, and DIYers calculate spindle gaps with precision.

This calculator is based on standard building codes and offers multiple spacing methods. It supports both imperial (inches, feet) and metric (mm, cm, meters) units, making it useful for users worldwide.

What Is Spindle Spacing?

Spindle spacing refers to the gap between vertical balusters or spindles on railings, staircases, or decks. The spacing must be equal and meet local building codes, which often require that the gap does not exceed 4 inches (100mm) to prevent accidents.

Accurate spacing ensures safety, uniformity, and compliance with building regulations. It also improves the look and balance of your structure.

How Does the Spindle Spacing Calculator Work?

Our Spindle Spacing Calculator uses three accurate methods to suit different needs:

Even Spacing Method

This method evenly distributes spindles across the entire length. It adds one extra space between the spindles and the end posts.

Formula used:

Spacing = (Distance between posts - (Number of spindles × Spindle width)) ÷ (Number of spindles + 1)

This ensures equal spacing across the entire railing, including the gaps at both ends.

Centered Spacing Method

Centered spacing creates equal end gaps and ensures no spindle is too far apart by using a maximum allowed gap (e.g., 4 inches or 100mm).

Steps used:

  1. Unit Length = Spindle width + Maximum spacing
  2. Number of spindles = Floor(Distance ÷ Unit Length)
  3. End Gap = (Distance − (Number of spindles × Unit Length) + Max spacing) ÷ 2

This layout balances all gaps, making it ideal for modern and aesthetic finishes.

Slanted (Stair) Spacing Method

When working with stairs, the angle affects spacing. Our calculator adjusts horizontal spacing based on the stair pitch.

Formula used:

Slanted spacing = cos(Angle in degrees) × Horizontal spacing

Where

Horizontal spacing = (Distance − (Spindles × Width)) ÷ (Spindles + 1)

This ensures safety and balance on staircases where the horizontal distance visually appears shorter.

How to Use the Spindle Spacing Calculator

Using the calculator is simple:

  1. Enter the total distance between posts.
  2. Choose the unit (in, mm, cm, ft, or m).
  3. Enter the spindle width and select its unit.
  4. Choose a method: Even, Centered, or Slanted.
  5. For even or slanted, enter the number of spindles.
  6. For centered, enter the maximum spacing allowed.
  7. If using slanted spacing, enter the stair angle.
  8. Click “Calculate” to get results instantly.

The tool will show your spacing in your selected unit and highlight whether it meets standard building codes.

Final Verdict

Our Spindle Spacing Calculator is designed to take the guesswork out of your project. With support for metric and imperial units, and options for even, centered, or stair spacing, it’s the ultimate tool for homeowners and professionals alike.

Whether you're planning a new deck, updating a staircase, or adding railings to a balcony, this calculator ensures you stay within code and maintain perfect visual symmetry.

Avoid spacing errors, rework, or failed inspections. Try our calculator today — it’s fast, accurate, and completely free to use.

Frequently Asked Questions (FAQs)

How to calculate space between spindles?

You subtract the total width of all spindles from the total distance and divide the remaining space by the number of gaps. For centered gaps, you calculate using unit lengths and end gaps.

How far apart should spindles be?

Building codes usually require spacing to be 4 inches (100mm) or less to ensure child safety.

How many spindles do I need per foot?

On average, you’ll need about 2.5 to 3 spindles per foot, depending on the spindle width and gap.

Can I use this calculator for stairs?

Yes. Use the Slanted method and input your stair angle to get accurate spacing along the diagonal.

What is the code spacing for horizontal balusters?

Most codes state that a 4-inch sphere should not be able to pass between any gaps, whether vertical or horizontal.

Does this work with metric units?

Absolutely. You can choose between millimeters (mm), centimeters (cm), meters (m), inches (in), or feet (ft).