How to Calculate Run-Over-Rise to Make Stairs

Stairs are a convenient way to get from one level to another, but poorly planned and built stairs can cause accidents and make moving between levels more difficult. The relationship between the height and length of each step makes the difference between a stair that is easy to navigate, and one with a high nuisance factor. Stairs are important enough to construction that many countries have codified the requirements to give people safe passageway.

Measuring tape

Instructions

- 1
  Determine the use of the steps. A stair with a longer run and shorter rise takes more room, but is easier to walk up than one with a short run and longer rise. Moving material up and down a longer run is easier, and those who have difficult with steps often prefer a longer run with shorter rise.
- 2
  Measure the height of the run and divide this by the riser height to determine the number of stairs. For example; if the distance from one floor to the next is 60 inches, and you desire a riser height of 7 inches, the total number of steps is 7 divided into 60, or 8.57 steps. Rounding to the next highest number yields 9 steps between the levels, counting the floor itself and the upper landing as steps.
- 3
  Divide the total rise with the actual number of steps to give the actual riser height. In the example, 9 stairs divided into 60 inches gives us an actual riser rate of 6.66 inches.
- 4
  Subtract 6.66 inches from 17.5 inches to get the estimated run of 10.84 inches. Both measurements are well within acceptable building codes and give the stairs an approximate 30-degree angle.

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