Stair calculator
Calculate the number of risers, tread depth and stair angle for a given total rise.
Stair calculator
Calculate the number of risers, tread depth and stair angle for a given total rise.
Enter your staircase dimensions to see the estimate.
Stair layout
Project summary
How it works
These are estimates for planning. Actual stair dimensions are subject to local building codes. Verify requirements before building.
Stair calculator
This is a geometry tool, not an engineering tool
This calculator works out the math of how many steps fit a given rise, what each riser and tread will be, and what angle the stairs make. It does not account for local building codes, which set minimum and maximum riser and tread dimensions, nor for structural requirements like stringer thickness, load capacity, or handrail height. Use it to plan the layout, then verify against your local code before building.
Riser and tread are related
The riser is the vertical face of each step. The tread is the horizontal surface you step on. The number of risers equals the number of steps; the number of treads is one less because the top step lands on the upper floor, which is not a tread. The rule of thumb for comfortable stairs is a riser between 7 and 8 inches and a tread between 10 and 11 inches, which is what the calculator defaults to.
The angle matters for comfort and safety
Stairs between 30 and 38 degrees are comfortable for most people. Below 30 degrees starts to feel like a ramp; above 40 degrees starts to feel like a ladder. The calculator shows the angle so you can judge whether the layout is comfortable before you cut any wood.
Frequently asked questions
How do I calculate stair rise and run?
Divide the total rise by the desired riser height to get the number of risers, then round to a whole number. Divide the total rise by the rounded number of risers to get the actual riser height. Multiply the number of treads (one less than risers) by the desired tread depth to get the total run. The calculator does this automatically.
What is the standard stair angle?
Between 30 and 38 degrees is the comfortable range for residential stairs. The International Residential Code specifies a maximum riser height of 7.75 inches and a minimum tread depth of 10 inches, which produces angles in that range for typical residential rises. Always check your local code.
How many steps do I need for a 10 foot rise?
At a 7 inch riser height, you need about 18 steps. The calculator gives you the exact count based on your total rise and riser height.
What is the standard riser height for stairs?
Most building codes require risers between 4 and 7.75 inches. 7 inches is a common residential standard. The calculator lets you enter any riser height.
How long should the treads be?
Standard residential treads are 10 to 11 inches deep. The calculator computes the total run based on your tread depth and number of steps.
Do I need a landing?
Most codes require a landing at the top and bottom and a intermediate landing if the stairs change direction. The calculator computes the straight run, and you add landing requirements separately.
How many stringers do I need?
Two stringers are standard for stairs up to 3 feet wide. Wider stairs need three or more. The calculator gives you the step count, and you determine stringers based on width.
What angle should stairs be?
Most residential stairs are 30 to 35 degrees. The calculator shows the stair angle automatically based on your riser and tread dimensions.