Measuring Guide

Free Resource · All Things Stairs

How to Measure
Your Staircase

Order the right parts the first time, every time. Step-by-step measurements, diagrams, and code requirements — all in one place.

In This Guide
1Staircase Anatomy 2Rise & Run 3Baluster Spacing 4Handrail Height 5Newel Post Sizing 6Quick Reference
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Section 01

Staircase Anatomy

Know the name of every part before you shop — it avoids confusion when ordering and ensures you get exactly what you need the first time.

Staircase with labelled parts: tread, riser, nosing, baluster, handrail and newel post
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Numbered pins identify each staircase part — descriptions below
1
Tread
The horizontal surface you step on. Typically 10–11" deep, measured nose to nose.
2
Riser
The vertical face between two treads. Typically 7–7.75" tall. All risers must be within 3/8" of each other.
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Nosing
The overhanging front lip of each tread. Code maximum: 1.25" overhang beyond the riser face.
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Baluster
Vertical spindles between tread and handrail. Max 4" gap between each — always check your local code.
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Handrail
The graspable rail running along the staircase. Code height: 34–38" measured vertically from the tread nosing.
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Newel Post
The anchor post at the top and bottom of the stair. Height is set by handrail height plus your desired space above the rail.
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Pro Tip
Take a photo of your staircase from the side before measuring — send it to our team and we'll identify every part and confirm your measurements. It's free and no obligation.
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Section 02

Measuring Rise & Run

Rise and run are the two most critical numbers. Get these right and everything else follows. Always measure in inches — never feet.

RISE 7–7.75" RUN 10–11" TOTAL RISE TOTAL RUN

Rise = vertical height per step  ·  Run = horizontal depth per tread  ·  Measure in inches

1
Measure Total Rise — floor to floor
Measure the vertical distance from the finished floor at the bottom to the finished floor at the top. Divide by the number of steps to get your rise per step.
IRC max: 7.75" per step Measure at least twice
2
Measure Total Run — face to face
Measure the horizontal distance from the face of the first riser to the face of the last riser. Divide by number of treads to get run per tread.
IRC min: 10" per tread Typical: 10–11"
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Important
Always measure in inches, not feet. If your stairs are carpeted, measure to the subfloor and note the carpet thickness separately when selecting tread thickness.
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Stair Calculator
Use the free stair calculator at calculator.net/stair-calculator.html to automatically calculate rise, run, and baluster quantities from your total measurements.
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Section 03

Baluster Spacing & Quantity

Building code sets the maximum gap between balusters — but always verify your local requirement before ordering. Nosing overhang, tread width, and spacing all affect your final count.

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Maximum Gap
The IRC sets a maximum of 4" gap between balusters. Always check your local building code — some jurisdictions require tighter spacing. When in doubt, go tighter.
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Balusters Per Tread
Typically 2 to 3 balusters per step, depending on tread width. Verify spacing requirements with your local building authority before placing your order.
How to Calculate Baluster Quantity
1
Measure tread width in inches (e.g. 36")
Account for any nosing overhang if desired — stair nosings should be no larger than a 1.25" overhang on a step. Factor this into your usable tread width.
2
Apply the formula
Divide tread width by your spacing (max 4"), subtract 1:
(Tread Width ÷ Spacing) − 1 = Balusters per tread
Example: 36" ÷ 4" = 9 spaces → 9 − 1 = 8 balusters per tread
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Multiply by treads — then add 10%
Always order at least 10% extra. Breakage during shipping and cutting errors happen. Custom pieces can take weeks to reorder.
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Pro Tip
Always round up your baluster count. A 4" gap is the legal maximum — slightly tighter spacing looks better and keeps you comfortably within code tolerance.
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Section 04

Handrail Height & Profile

The handrail must be graspable and sit at the correct height above the tread nosing. This measurement also determines your newel post height — get it right first.

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Code Height
Measured vertically from the tread nosing to the top of the handrail: 34" to 38". Measure at multiple points along the run.
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Graspability
Round or oval profiles between 1.25"–2" in diameter are ideal. Flat-top rails need a graspable return edge or they'll fail inspection.
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Measuring Length
Measure the sloped length newel-to-newel along the angle. Add 6–12" per end if the rail returns to a wall. Always round up.
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Matching an Existing Profile
If you're matching an existing handrail, trace the profile on paper or send us a photo. We stock all major profiles — Traditional, Moulded, and Wrap Rail — and can help you match exactly.
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Section 05

Newel Post Sizing

Newel post height isn't a fixed number — it's determined by your handrail height and how much post you want above it. Here's how to think about it correctly.

How Newel Post Height Is Determined
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Start with handrail height — this is your foundation

Code requires the handrail to sit 34"–38" above the tread nosing, measured vertically. This is non-negotiable and sets the minimum height your post must reach.

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The post must support the handrail at the code height

The handrail attaches to the post at the 34"–38" mark. Your post needs to be at least this tall to support the rail correctly.

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How much post shows above the handrail — your design choice

There is no code minimum for the space between the top of the handrail and the post cap or top of the post. This is purely a stylistic decision. More extension above the rail = more traditional look; flush or minimal = contemporary.

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Width: match to baluster visual weight

Common sizes: 3.5", 4.5", and 5.5" square. Wider balusters call for a wider newel to maintain proportion.

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Box Newel
Square post with decorative panels. Most common for traditional and colonial-style homes.
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Turned Newel
Lathe-turned round post with decorative profiles. Classic, cottage, and Victorian styles.
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Modern Newel
Clean square or rectangular post with minimal detailing. Contemporary and industrial spaces.
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Pro Tip
When replacing a newel post, take a rubbing of the base plate bolt pattern before removing the old post. This ensures your new post bolts directly into the existing anchor without any subfloor modification.
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Section 06

Quick Reference Cheat Sheet

Bookmark this. Everything you need before placing your order — at a glance.

Measurement Typical Range Code Requirement Notes
Rise per step 7" – 7.75" Max 7.75" (IRC) All risers must be within 3/8" of each other
Run per tread 10" – 11" Min 10" (IRC) Nosing overhang max 1.25"
Handrail height 34" – 38" 34"–38" from nosing Measured vertically from tread nosing to top of rail
Baluster gap 3" – 4" Max 4" gap (IRC) Check local code. Typically 2–3 balusters per tread.
Newel post height Varies Design choice above rail Post must reach handrail height (34"–38" from nosing)
Post width 3.5" / 4.5" / 5.5" No code requirement Match to baluster visual weight and stair width
Order quantity Calculated + 10% — Always order 10% extra for breakage and cuts
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Industry Resources
Stair Calculator: calculator.net/stair-calculator.html
Code & Technical Standards: stairways.org — stairs.com is a proud member of the Stairbuilders & Manufacturers Association (SMA).
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