Stair Pro is a calculation tool only. All results are estimates based on your inputs. ProBuilder Apps assumes no liability for the use, misuse, or reliance on any calculations provided by this app.
It is the user's sole responsibility to verify all dimensions, materials, and measurements comply with local building codes and regulations before construction.
By using this app, you accept full responsibility for any decisions made based on its output.
StairPro
Stringer Calculator
Stair Parameters
Total Rise
Total Run (Optional)
Use Total Run only when stairs must fit a fixed space. Results may not meet building code requirements. Stairs calculated using this feature may be unsafe and non-compliant. Use at your own risk.
Unit Dimensions
Unit Rise is the height of each step. Enter your desired rise per step — the app will calculate the exact adjusted rise needed to evenly divide the total rise. Unit Run is the horizontal depth of each step — the flat surface where your foot lands. Together they determine the stair's pitch and comfort.
Material Thickness
Stringer Lumber
2×12 is recommended for most applications — it provides a stronger throat after cutting. 2×10 may work for shorter runs with lower rises. The throat (narrowest point after cutting) must be at least 3.5 inches. Consult your local building code.
Stringer Waste
Adds extra length to account for cracked or damaged lumber ends — cut and discard the bad end, still have enough material.
Width & Stringers
Number of stringers across the stair width. Check your local building code for minimum requirements.
Tread Lumber
Stair Results
Risers
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Treads
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Adj. Rise
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max 7¾" per code
Stringer Length
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Total Run
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Pitch Angle
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30°–37° ideal
Rise + Run
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17"–18" ideal
Headroom
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min 6'8" req
Rise Cut
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framing square mark
Run Cut
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framing square mark
Top Mount
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Tread Boards
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Tread Waste
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IBC / IRC Reference: Max riser 7¾", min tread 10", rise+run 17–18" ideal. Nosing ¾–1¼". Handrail 34–38". Check local codes.
Riser Count Note: Riser count includes the final rise onto the deck/landing. The deck surface acts as the last tread. Your stringer will have one fewer tread cut than riser cuts — the top rise is where the stringer connects to the deck.
Exports stair results as a professional PDF.
Side Elevation
This diagram does not show tread nosing overhang. Per IRC R311.7.5.3, a nosing projection of ¾" to 1¼" is required on treads with solid risers. Allow for nosing overhang during assembly and verify requirements with your local building code.