Stair Stringer & Step Calculator
Enter your total rise and run to get exact riser height, tread depth, stringer length and angle — with a building code compliance check against IRC (US), UK Part K, or AS 1657 (Australia). Nothing uploaded.
Stringer Diagram
Results
Learn more: stair stringer design
Why deck stair geometry matters
Stairs that are too steep are dangerous. Stairs with inconsistent riser heights (even by 5mm) cause people to trip because their muscles expect a consistent step. Building codes set maximum riser height and minimum tread depth for exactly this reason - and inspectors do check deck stairs on permit projects. The calculator shows the SVG side-elevation diagram updating live so you can see the geometry of your stringer before you make a single cut.
Stringer dimensions in three steps
First, enter total rise and run - total rise is the height change and total run is the horizontal distance, in mm or inches. Second, set step count or target riser by entering either a step count (and the calculator works out riser height) or a target riser height (and it computes how many steps fit). Third, read stringer geometry and code check - riser height, tread depth, stringer board length, stringer angle, and IRC/UK/AU code compliance badge.
FAQ
What is the maximum riser height allowed by building code?
Under IRC (International Residential Code, used in most of the USA), the maximum riser height is 7-3/4 inches (196mm) and the minimum tread depth is 10 inches (254mm). UK Building Regulations Part K allow a maximum 220mm rise and minimum 220mm going. The calculator checks compliance against the code you select.
How do I calculate stringer length?
Stringer length is the hypotenuse of the triangle formed by the total rise and total run: sqrt(rise² + run²). The calculator computes this automatically and adds the necessary length for the top and bottom landing connections.
How many steps do I need for a given rise?
Divide the total rise by your target riser height. For example, a 900mm total rise with 175mm risers gives 900/175 = 5.14, which rounds to either 5 or 6 steps. The calculator shows all valid step counts and highlights the one with the closest-to-ideal riser height.