Stair Calculator

Calculate rise, run, stringer length, and IBC code compliance for any staircase.

Total rise (inches)

Preferred rise per step (inches)

Preferred run per step (inches)

Our stair calculator helps you determine the optimal step layout for both standard and custom step dimensions. It takes the total rise and preferred riser/tread dimensions to calculate the number of steps, total run, and stringer length. Also, it compares the results against IBC code limits, so you know if it will pass inspection.Once you know the layout of your stairs, you can quantify the materials needed. With Houzz Pro’s material Cost Catalog, you can pre-program material and labor costs to make estimating quick and easy. You can also use our Clipper tool to get real-time costs directly from your preferred vendors’ websites.

How to calculate stair dimensions

Here’s a short stair glossary:

Total rise – Vertical distance from floor to floor
Stair rise – Vertical distance from stair to stair
Riser – Vertical part of a stair
Total run – Horizontal distance the stairs travel
Tread run – Horizontal depth of steps
Tread – Horizontal part of a stair
Stringer – Diagonal support board

Here’s how to calculate stair dimensions:

Start with the total rise (measured from finished floor to finished floor) and desired stair rise (usually 7-7.5 inches) and run (usually 11 inches).
Divide the total rise by the desired stair rise to get the approximate number of stairs needed. Round to the nearest whole number.
Divide the total rise by the whole number of stairs from above to get the exact height of each stair.
There are a few ways to calculate tread depth or run:
Code requirements (minimum is usually 10 inches)
7-11 rule (7-inch rise, 11-inch tread)
17-18 rule (sum of one rise and one run should be between 17-18 inches)
Blondel’s formula ((2 x rise) + tread = 24 to 27 inches)
Multiply the number of treads (usually 1 less than the number of risers) by the tread depth to calculate the total run. (# of risers – 1) x tread depth = total run
The stair stringer calculation requires the use of the Pythagorean theorem. Stringer length is equal to the square root of the total rise (squared) plus the total run (squared). You’ll want to add 1 inch to the stringer length when cutting to allow for a plumb cut on the bottom tread.

Note that IBC requires stair risers to be 4-7 inches and stair treads at least 11 inches. Check the local code if you plan to do something different.All risers in a stairway must be within 3/8 inch of each other, or it will fail inspection.Here’s an example showing how our stair calculator determines the dimensions and layout for a staircase with a total rise of 112 inches, a preferred stair rise of 7 inches, and a preferred stair run of 11 inches.Calculator inputs:

Total rise: 112 inches
Preferred rise: 7 inches
Preferred run: 11 inches

Based on the inputs above, the calculator provides the number of steps, the actual rise and run, the total run, and the stringer length. It also indicates whether the staircase complies with the IBC code. Here’s the breakdown:

Number of steps: 16
Actual rise per step: 7 inches
Actual run per step: 11 inches
Total run: 14.7 feet
Stringer length: 17.38 feet
IBC compliant: Yes

For greater estimate accuracy and time savings, use Houzz Pro’s Cost Catalog and Clipper tools when estimating projects.

Stair Calculator

How to calculate stair dimensions

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