Stair height calculator

The cleanest way to measure total rise is finished floor to finished floor: set a straight, rigid story pole or a long level at the lower finished floor and read the height where it meets the upper finished floor level.

A laser level set at the upper floor height, read against a tape held plumb at the lower floor, works just as well and is easier for one person to do alone.

Older houses in particular are rarely dead level. Take your height measurement at the actual location the stair will land, not from a random spot in the room, since a floor that's out of level by even ½ in over a run changes your total rise at that specific point.

A story pole, a straight board marked and cut to the exact measured height, is worth the extra ten minutes. It lets you double-check your number by simply holding it in place a second time before you commit to cutting stringers.

1. Set a story pole or level at the lower finished floor, at the exact spot the stair will land.
2. Extend it up to the upper finished floor level.
3. Mark and measure that length; this is your total rise.
4. Repeat at the opposite side of the stair opening if the opening is wide, and use the larger reading if they differ.

If finished flooring isn't installed yet, you have two options: measure to subfloor and add the planned flooring thickness on both levels, or wait until flooring is down to measure for real. The first option is faster but riskier if flooring plans change.

A common failure case: subfloor-to-subfloor reads 100 in, but ¾ in hardwood goes down on the upper floor only. Real total rise becomes 100.75 in, enough to throw a 13- or 14-riser stair's riser height outside commonly cited variation limits if it isn't accounted for up front.

Total height doesn't just influence riser count, it determines it, once you've picked a target riser height. There's no flexibility to add or remove a riser without changing the actual riser height for the whole flight.

This is why height should be the very first number you lock down on a stair project, before you shop for tread stock or think about railings.

Using a 7¼ in target riser height as a starting point:

Outdoor height measurements need the same finished-surface logic, but the lower point is grade or a landing pad rather than a subfloor. Measure to finished grade if it's already established, or to where grade will be once site work is done, not to the current, unfinished ground.

Once you have your height and riser count, add a tread depth on the stair rise and run calculator to work out total run, or check the stair run calculator if floor space, not height, is your limiting factor.