Stair & stringer guide · 4 min read
How to calculate the first stringer rise
Learn why tread thickness is subtracted at the bottom stringer cut so every finished stair riser remains equal.
Why the bottom cut is different
The stringer layout describes the rise from one framing notch to the next, but the finished tread sits on top of each notch. At the first step, that added tread thickness would make the finished rise too tall unless the bottom of the stringer is shortened by the same amount.
This is a correction to the bottom vertical cut—not a change to every rise in the layout.
First stringer rise = exact finished riser − tread thickness
A simple example
If the exact finished riser is 7 1/2 inches and the finished tread is 1 inch thick, the bottom vertical cut on the stringer is 6 1/2 inches. Once the 1-inch tread is installed, the first finished rise is 7 1/2 inches—matching the others.
Avoid the common mistakes
- Do not subtract tread thickness from every riser notch.
- Use the actual finished tread thickness, not the nominal lumber name.
- Include flooring or landing finishes in the original total-rise measurement.
- Recalculate if the tread material changes after layout.
- Check the first and last finished risers before cutting the remaining stringers.
The calculator reports this corrected first stringer rise automatically when you enter tread thickness.