How To Figure And Calculate Stair Run

There are two ways you can figure out and calculate the stair run of a stairway. The first is to use a measurement that will keep the stairway within specific boundaries and the second will be to start with a specific individual stair tread size and multiply it by the number of steps, in the stairway.

The total stair run is the distance between the front of the upper floor and the nosing on the first step.

This measurement will be the same at the bottom of the stairway, in the middle of the stairway and at the top of the stairway.

The green vertical lines in the illustration above represent the front of each individual stair tread run, not the over all stair tread run, the individual stair tread measurement is also referred to as the stair run or the run of the stairs, just don't mix it up with the overall or total stairway run.

I don't make the rules, so give me a break. This wasn't the first and it isn't going to be the last thing that confuses you, throughout your lifetime.

In the illustration above I removed the stair stringer, but left the individual 10 inch stair tread measurements and the vertical lines, to give you a better idea, how you can figure out the overall stair tread run, by using individual stair treads, instead of an overall measurement.

This is the most common way to figure out the total staircase run. Architects and designers will usually use a 10 inch measurement for each individual stair tread and multiply it by the amount of stair treads required, to build the stairway.

The total stair run in the illustration above is 40 inches

In the illustration above, I simply transferred the 10 inch individual stair tread measurements down to the floor, to provide you with a better idea, what I'm talking about.

The illustration above provides you with the total stairway run, without any stairs or measurement marks. This is what you would be starting with, if you were building a stairway from scratch.

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