Stair Calculator

About the Stair Calculator

Calculates the number of steps, riser height and tread depth for a staircase from the total rise and run, and checks comfort guidelines.

How to use this calculator

1. Enter the total vertical rise from the finished lower floor to the finished upper floor, in the same unit you want the result in.
2. Enter the desired number of steps or let the calculator estimate a good count from standard stair rules.
3. Check the riser height, which is the height of each step, and the tread depth, which is the horizontal part you step on.
4. Review the layout so the stairs fit your space and meet local building code requirements.

The formula explained

The calculator uses the total rise and the number of risers to find each riser height, then uses the stair run and the number of treads to find each tread depth. In simple form, riser height is \(\frac{\text{total rise}}{\text{number of risers}}\), and tread depth is \(\frac{\text{total run}}{\text{number of treads}}\).

• total rise = the vertical distance from the lower floor to the upper floor
• number of risers = the total count of vertical step heights
• riser height = the height of one step
• total run = the horizontal distance the staircase covers
• number of treads = the total count of stepping surfaces
• tread depth = the depth of one step

Step by step method

1. Measure the total rise from finished floor to finished floor.
2. Choose the number of risers so each step height is comfortable and close to code limits.
3. Find the riser height using \(\frac{\text{total rise}}{\text{number of risers}}\).
4. Find the tread depth using \(\frac{\text{total run}}{\text{number of treads}}\), then check that the stairs fit the available space.

Worked example

Problem. A staircase has a total rise of \(108\) inches and a total run of \(120\) inches. If you use \(6\) risers, what are the riser height and tread depth?

1. Riser height is \(\frac{108}{6} = 18\) inches.
2. For \(6\) risers, there are typically \(5\) treads, so tread depth is \(\frac{120}{5} = 24\) inches.
3. The staircase has a riser height of \(18\) inches and a tread depth of \(24\) inches.

Tips and common mistakes

• Make sure all measurements use the same unit, such as inches or centimeters.
• A common mistake is counting risers and treads the same way, but the number of treads is often one less than the number of risers.

Frequently asked questions