How to measure stair stringer angle
If you have a stair photo, a plan, or a drawing screenshot, you can measure the stringer (slope) angle in the browser. Align a true horizontal reference first, then read degrees.
When this helps
Use this when you need the stair slope angle for layout checks, documentation, or comparing to a plan. Plans/drawings usually measure cleaner than camera photos.
Step-by-step
- 1Get a clean stair stringer viewPrefer a plan/blueprint or a drawing export. For photos, capture a clear side profile of the stairs and avoid perspective tilt.
- 2Upload or paste the imageOpen the tool and add the image (upload, drag & drop, or paste).
- 3Align a true horizontal baselineRotate/flip and use the grid so a known level edge becomes perfectly horizontal (floor line, plan axis, or a level reference).
- 4Measure along the stringer lineMove the center to the intersection where the slope starts. Keep the baseline on horizontal, then rotate to match the stringer (or nosing line) and read the angle.
- 5Verify and exportIf the reading looks off, re-check baseline alignment and vertex placement. Export PNG/PDF to document the stringer angle.
Tips
- Use the longest straight segment you can see (stringer edge or a consistent nosing line). Short segments amplify placement error.
- Photos can bias the angle if shot from above/below. A plan or a screenshot from a drawing is often more reliable.
- Zoom in when placing the vertex and aligning the stringer line; small offsets can shift the reading.
Related
Measure an angle on a blueprint
Use this when the stair slope comes from a plan or construction drawing.
Measure an angle from a camera photo
When you only have an on-site photo, prioritize alignment to reduce perspective error.
PNG and PDF exports
Save a shareable image or a report once the stair angle is correct.
Angle looks inaccurate
Common causes: perspective distortion, baseline misalignment, and vertex placement.