Deck Stair Geometry Calculator
Enter your total rise and a target riser height to get an even riser count, actual riser height, and tread layout.
Vertical distance from the ground to the deck surface.
Your starting point — the calculator finds the closest even split.
Riser count
5
- Actual riser height
- 7.2 in
- Tread count
- 4
- Horizontal run
- 3.33 ft
- Approx. stair angle
- 35.8°
›Calculation details
This calculator assumes the deck surface acts as the final upper landing, so tread count is one less than riser count.
Riser count rounds your target riser height to the nearest whole number of even steps, then the actual riser height is recalculated so every step is identical.
How it works
Stairs need every riser to be the same height, so this calculator rounds your target riser height to the nearest whole number of steps that evenly divides the total rise, then reports the actual height each step ends up at — which is often slightly different from what you originally typed. Tread count is one less than the riser count, since the deck surface itself serves as the top landing.
FAQ
Why is my riser height different from what I entered?
Your target is a starting point, not the final answer — the total rise has to divide evenly across a whole number of identical risers, so the actual height is whatever makes that work out exactly.
Does this tell me if my stairs are up to code?
No — maximum riser height, minimum tread depth, and stringer sizing are all set by your local building code and aren't checked here. This tool only works out the geometry from the numbers you enter.