Baluster Calculator: How Many Balusters Do I Need?

A group of teenage girls running down the stairs
Photo: Klaus Vedfelt / DigitalVision / Getty Images
A group of teenage girls running down the stairs
Photo: Klaus Vedfelt / DigitalVision / Getty Images
Melissa Graham
Written by Melissa Graham
Contributing Writer
Updated Jun 3, 2025
Highlights

  • The number of balusters you need depends on the length of your railing. 

  • End spacing and your desired spacing between balusters are also important. 

  • If you prefer not to lean on your calculations, a pro can do it for you. 

  • Your local stair and railing installer can do the baluster calculations and installation.

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How many balusters do I need for my deck or stair railing? It’s not rocket science, but it does require a bit of measuring and math. We’re here to guide you through what measurements to take and how to incorporate them into a baluster calculator that can spit out exactly how many balusters you need in no time. 

How Many Balusters Needed For Railings

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No need to eyeball it (and actually, we highly suggest going against that route)—instead, here’s a handy cheat sheet that will help you nail your baluster count. Note that this assumes a 2-inch end spacing on both ends, with calculations rounded down to the nearest whole baluster.

Railing Length (feet)Spacing Between Balusters (inches)Number of Balusters Needed
5416
10430
16448
18454
20460
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Calculating Balusters

Walk-out deck with wooden railing balusters
Photo: irina88w / iStock / Getty Images Plus / Getty Images Plus

Using your railing size and end spacing measurements, apply the following formula to determine how many balusters your railing needs:

Number of balusters = (Railing length – 2 x End Spacing) / Spacing between balusters

How to Measure Railing Length and End Spacing

You can’t determine how many balusters you need without measuring the length of your railing as well as the spacing between its ends. Read the tips below to make sure you get both right the first time around. 

How to Measure Railing Length

A simple tape measure can get you through this quick task, which entails measuring the length of your railing from the end of one post to the end of another. If you’re dealing with a stair railing, make sure to measure the horizontal projection instead of the diagonal length. 

How to Measure End Spacing

End spacing is the distance from the edge of the railing or post to the center of the first and last baluster. This keeps your deck or staircase symmetrical versus looking like you eyeballed it over brunch. Here are some tips on how to measure end spacing: 

  1. Decide how much space you want between each baluster. 

  2. Divide the spacing in half. This is your end spacing. 

  3. Measure 2 inches in from the inside of each post. 

  4. This is where the center of your first and last baluster will go. 

Who to Hire to Install Balusters

Your local stair and railing contractor is the ideal candidate to install balusters on your outdoor deck or in your interior stair railing. If you’re at the beginning stages of the project, they can also come out and measure the area in need to determine how many balusters you need. Only homeowners who are skilled carpenters and have extensive experience in carpentry should attempt to DIY baluster installation.

Frequently Asked Questions

Balusters provide vertical support to make sure your stair railing and/or deck is as sturdy and safe as possible. These spindles help hold up the railing so people walking up or down stairs have something strong to hold onto. They can also act as a unique design element if they’re custom-made to suit a specific style or size requirement.

The cost to install a stair railing ranges from $500 to $1,300, depending on the size of the railing and what type of materials are used. The bigger and more custom the project is, the more likely your project is to fall closer to the $1,300 end of the spectrum.

Wood is a very versatile material, so you can either compost it, use it for firewood, turn it into wood chips, or save it for future projects. If you don’t want excess wood cluttering your garage or workspace, you can call local community centers or schools to see if they have a need for it.

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Learn more about our contributor
Melissa Graham
Written by Melissa Graham
Contributing Writer
Melissa has spent over ten years writing about home design, style, and DIYs for regional and national publications.

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