Rail length along the rake, end returns, and a height check against your code.
The graspable rail runs the diagonal length of the flight (the rake), plus end extensions or returns required for safety. Height is measured vertically from the tread nosing line and must sit within the code band.
At least the diagonal length of the flight, plus any required top and bottom extensions or returns. Commercial codes often require a 12-inch extension at the top and one tread-depth plus 12 inches at the bottom.
Between 34 and 38 inches above the tread nosing line under the IRC and IBC.
Many codes require the rail to return to the wall or post at each end so clothing or bags cannot catch on an open end.