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How to Calculate Your Deck Baluster Count and Spacing


Designing the right railing setup can transform your deck. If you’re replacing a current railing system or building a new railing from the ground up, there are a wealth of deck railing options available, from metal railing systems to cable railing lines to composite deck railings and more.

But it’s not just new railing setups that offer a huge range of options. If you’re looking to spruce up your existing railing, you can also swap out your current balusters or upgrade to metal deck balusters. With round and square profiles, and between-rail or face-mount attachment options, creating the outdoor space you've always wanted has never been easier!

Whether you’re building a new railing or refreshing your existing setup, DecksDirect is here to help you plan out your deck baluster spacing with this handy guide.

DecksDirect Baluster Calculator Tools

For quick and easy reference, we’ve created two helpful tools to help you calculate how many balusters you’ll need for a section of railing. If you want to learn more about the math behind our baluster calculator, we’ll break down the full process below.

Deck Baluster Calculator

Find the DecksDirect Baluster Calculator Here

This handy tool will help you determine how many total balusters you’ll need in a specific section of railing.

To use the tool, you’ll need to take four measurements:

  • Total length of railing (Including posts)
  • Total number of posts
  • Size of posts
  • Size of balusters

Plug in each measurement and click “Calculate” - our tool will do the math for you, with the number of balusters needed appearing in the bottom box.

Deck Baluster Spacing Calculator 

Find the DecksDirect Baluster Spacing Calculator Here

Once you know the number of balusters needed, the Spacing Calculator will help you space them evenly across your railing while complying with building codes.

Simply enter the total length of your railing and the calculator will give you a personalized chart showing you where to place each baluster in your setup.

Table of Contents:

Baluster Count & Spacing Explained

Planning the design and layout of your railing is crucial for any deck project. That includes knowing how many balusters, sometimes called spindles, you’ll need per railing section, and how to space them for a symmetrical look. It’ll take a little bit of basic math, but don’t worry - we’ve put together a simple, step-by-step guide to make things as easy as possible.

We know most people don’t miss their days of doing math homework. Unlike your junior high algebra teacher, DecksDirect doesn’t require you to show your work - in fact, we don’t even require you to do the work. If you’re confused about any step of the process, give us a call at 1-888-824-5316 and our team will help you take the right measurements, then run the numbers for you.

This short video lays out the baluster spacing process, and we’ve also summarized the steps below. As always, remember to check your local building codes before starting any installations.

Here’s a brief recap of the steps we lay out in the video above. It calls for a handful of math calculations - if you’re confused at any point, you can always give us a call at 1-888-824-5316 and our team will guide you through the measuring and calculating process.

How Many Balusters Do I Need For My Deck Railing?

Figuring out how many balusters you need will require a couple of measurements and a handful of simple calculations. Follow the steps below:

What you’ll need:

  • Calculator
  • Tape measure
  • Paper
  • Pencil

Measuring Actual Rail Length

Measure the total length of your rail from post to post. Subtract the width of one baluster to find your Actual Rail Length.

  • Total Rail Length - Width of one baluster = Actual Rail Length

Determining Unit Width

Think of your railing in units. Each “unit” is a baluster and the space between it and the next baluster. Your Unit Width, then, is the width of one baluster and the space between two balusters. Building codes require a baluster spacing of no more than four inches - that means your balusters cannot be more than four inches apart.

We’ll use Unit Width to calculate several other key dimensions for your railing. 

  • Baluster width + space between two balusters = Unit Width

Determining Amount of Units

So how many units (a baluster and its space) will your railing need? To calculate, take your Actual Rail Length divided by your Unit Width.

  • Actual Rail Length ÷ Unit Width = Amount of Units

Determining Remaining Space

Now, we need to calculate how much space will be left at each end between the last baluster and the post. This will take a couple of steps.

First, we’ll calculate Used Space, or the distance between the first and last baluster in your railing. Take the whole number included in your Amount of Units - for example, if your Amount of Units is 13.9, take the 13 - and multiply it by your Unit Width. This will give you your Used Space.

Next, subtract your Used Space from your Actual Rail Length to find your Remaining Space. Divide the Remaining Space by two to determine how much space you’ll leave on each end of your railing between the last baluster and the post.

  • Whole number within Amount of Units x Unit Width = Used Space
  • Actual Rail Length - Used Space = Remaining Space
  • Remaining Space ÷ 2 = Space between last baluster and post on each side

If your first and last balusters look like they’ll be too close to your posts, you can go back to the beginning and change your baluster spacing to create a more even-looking baluster spread.

Determining How Many Deck Balusters You Need

Finally, we can use the calculations we’ve made to figure out once and for all how many balusters you’ll need for this section of your deck railing.

If the whole number in your Amount of Units is odd, then you’ll have a space in the center of your rail section. If the whole number in your Amount of Units is even, then you’ll have a baluster directly in the center of your rail section.

Round your Amount of Units up to the nearest whole number - that will give you the total number of balusters you’ll need for this rail section.

  • Round Amount of Units up to nearest whole number = Total Number of Balusters

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