How to Lay Out Stair Stringers

Formula

stringer_length ≈ √(total_rise² + total_run²). Angle = arctan(rise/run).

Units

Riser and tread in inches on the square. Overall rise/run in inches or feet consistently.

Step-by-step

1. Lock exact riser height and tread depth from the rise/run guide or calculator.
2. Set framing square tongue/tread and blade/riser (or use stair gauges).
3. Walk the square along the stringer stock for each step; mark plumb and level cuts.
4. Drop the bottom riser by tread thickness if treads sit on the notches (common detail).
5. Cut one pattern stringer; test fit; then duplicate.

Example — 7.5″ riser, 10″ tread, 12 risers worth of geometry

Total rise = 12 × 7.5 = 90″. Treads = 11 → total run = 110″. Stringer length ≈ √(90² + 110²) ≈ 142.1″ ≈ 11′ 10⅛″. Angle ≈ 39.3°.

Bottom riser drop

If treads are 1″ thick and sit on the notches, cut the bottom riser 1″ shorter so finished risers stay equal.

Common mistakes

• Forgetting the tread-thickness drop on the bottom riser.
• Cutting all stringers before a dry fit of the pattern.
• Measuring along the slope for tread depth instead of horizontal run.

Practical notes

• Leave enough uncut depth below notches for strength — follow lumber and span rules.
• Use the feet-fraction calculator when square marks land on odd sixteenths.

Related calculator

Use the free Stair Stringer Calculator to run the same math with your field numbers.

Related tools

• Stair Stringer Calculator — Residential stringer layout from total rise and run.
• Feet & Fraction Calculator — Add, subtract, multiply, and divide construction measurements.

Related guides

• How to Calculate Stair Rise and Run — Find riser height, tread depth, and unit count from total rise.