DIY Stairs Calculator

Stair design and layout requires accurate horizontal and vertical measurements. When laying out stairs, be aware of building code concerns, the existing materials, the proposed stair materials and your timetable. Your new stair requires a fair amount of planning and coordinating to prevent expensive mistakes. In addition, site conditions, particularly for the outdoors, may restrict your design choices. This is where calculations and a formula are handy to determine stair height and size.

Tape measure
Drawing pad
Calculator

Instructions

- 1
  Measure the vertical rise for the future stairs in inches. This value determines how many risers you will need between levels. Write this down on a sketch pad.
- 2
  Measure the horizontal area between the two levels. This determines the tread count.
- 3
  Divide the total height of the vertical rise by a riser height approved by the local code to get your riser quantity. You may have to calculate several times, varying the riser height in1/8 inch increments, to arrive at a riser height that fits within the code guidelines and allows all risers to be a uniform height.
- 4
  Divide the total length of your stair run by your proposed tread depth to determine your tread number. You may have to calculate multiple times, differing the tread depths in 1/8 inch increments, until you arrive at a whole number of treads. Residential stair design typically requires tread depths equal to or greater than 10 inches. Commercial, industrial and institutional buildings or spaces generally require depths equal to or exceeding 11 inches.
- 5
  Add any required landings to your stair length in your calculations, if needed. Landings may be required if total stair height exceeds local building code or ordinance. Landings are designed to equal the stair width, at a minimum.

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