Tread – the horizontal component of a staircase or the step, the part you walk on. The tread rests on a riser – or the vertical component of a step.

Stair tread, stair parts, Stair Runner glossary

We refer to stair counts as the number of treads/number of risers. Example: a single run on a straight staircase with 12 treads has 13 risers. When there is a landing within the staircase, the thread/riser counts should be broken down by each flight or run. If those 12 treads were instead split into 2 sections, let’s say 5 and 7 – your count is 5 treads/6 risers + 7 treads/8 risers OR a total of 12 treads and14 risers. This is important when calculating linear footage required.

The total number of risers is always greater than the total number of treads.