Deck Stair Calculator
Calculate riser height, tread count, and stringer length for your deck project.
Standard (Last step below deck)
Flush (Last step level with deck)
Calculated Dimensions
Number of Risers:
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Actual Riser Height:
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Number of Treads:
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Total Run:
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Stringer Length (Min):
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Stair Angle:
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How to Use the Deck Stair Calculator
Building deck stairs requires precision to ensure safety and code compliance. This calculator helps you determine the exact measurements needed to cut your stringers and frame your staircase correctly.
Essential Measurement Definitions
- Total Rise: The vertical distance from the top of the deck surface to the ground (or landing pad) where the stairs will terminate.
- Riser Height: The vertical height of each individual step. Residential building codes typically mandate a maximum riser height of 7.75 inches.
- Tread Depth: The horizontal distance of the step where you place your foot. Codes usually require a minimum depth of 10 inches.
- Total Run: The total horizontal distance the staircase will occupy on the ground.
Safety Tip: Most local building codes require that the difference between the largest riser and the smallest riser in a flight of stairs does not exceed 3/8 of an inch. Our calculator provides a uniform riser height for all steps to meet this requirement.
Building Code Guidelines (IRC)
While you should always check with your local building department, the International Residential Code (IRC) generally follows these rules:
- Maximum Riser Height: 7 ¾ inches (196 mm).
- Minimum Tread Depth: 10 inches (254 mm).
- Minimum Stair Width: 36 inches (914 mm).
- Handrails: Required for stairs with 4 or more risers.
Example Calculation
If your deck is 36 inches high (Total Rise) and you want a target riser height of 7 inches:
- Divide Rise by Target: 36 / 7 = 5.14. Round this to 5 risers.
- Actual Riser Height: 36 / 5 = 7.2 inches.
- Number of Treads: 5 risers – 1 = 4 treads (for standard mount).
- Total Run: If your tread is 11 inches, 4 x 11 = 44 inches of horizontal run.