Carpentry & Stairs calculators
Stairs, stringers, lumber and framing.
About this calculator
The stair calculator works out the number of risers and treads, the exact riser height, the total run and the stringer length from your total rise. It checks the layout against the IRC and, for deck stairs, against the American Wood Council DCA 6 guide, and gives layout marks for cutting the stringers.
How to measure
Measure the total rise from finished floor to finished floor, the surfaces people actually walk on. If the flooring is not installed yet, add its thickness. For deck stairs, measure from the top of the deck boards to the surface where the bottom step will land. If the lower floor is not level, hold a long level off the upper edge and measure plumb down.
Before you start
- Check headroom before you cut. A beam or duct over the stair is the most common reason a layout has to change.
- Keep every step identical. Small differences in riser height are what make people trip.
- Find the lowest point of the floor or grade under the stair and within 36 inches of each open side. That is the point the guard and open-riser rules measure to.
- Stairs are a life-safety item: confirm the requirements and whether you need a permit with your building department before building.