Forgetting this is the most common reason for a failed inspection. The bottom of the stringer must be cut shorter than the other risers by the exact thickness of the tread material. This ensures all steps from floor to landing have equal rise heights. Missing this detail creates a dangerous first or last step that violates IRC R311.7.5.1's maximum 3/8" variance rule.

While not always explicitly enforced, engineering best practice requires at least 5 inches of solid wood at the stringer's narrowest point (the "throat"). Shallow cuts from aggressive rise/run ratios create weak spots that can crack or fail under load. A typical 2×12 with 7½" rise and 10" tread yields a 5.3" throat—safe. But pushing to 8" rise with 9½" tread reduces this to 4.2"—borderline unsafe.

Never trace a copy. A pencil line's thickness is enough to throw off your layout by 1/16" per step—which compounds across 12 steps into a ¾" error at the top. Always mark the first stringer directly from your square, then use that exact stringer as the master pattern for all others. Store it for future jobs with the same rise/run.

A slip-and-fall lawsuit can question your work years after the job is done. Can you prove your stairs met code? Field notes on paper get lost. Photos don't show the math. You need a digital record with timestamped calculations, compliance validation, and exportable documentation.

The modern professional doesn't just measure twice. They use digital tools to verify geometry and compliance before the saw ever starts. Input your total rise and run. Check the riser variance. Verify the throat depth. Screenshot the calculation. Then cut with confidence knowing the inspector will sign off.