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The overall length of the stair stringer along its slope.
Along the SLOPE, which is longer than either the rise or the going — it is the hypotenuse of the two. If you have the rise and run, this site's stringer length calculation gives it. Hole spacing is set out along this length, so a length taken in plan puts every hole progressively short of where it should be, with the error largest at the top.
The maximum allowed spacing between adjacent bolt holes.
This should come from your connection design (bolt capacity, edge distance, and gauge requirements) or project specification.
Bolt holes needed
12 holes
- Bays between holes
- 11
- Hole pitch, as drilled
- 1.5 ft
They open the calculator with your figures already in it
Steel Stair Stringer Bolt Hole Spacing Calculator: 12 holes — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Bolt hole count = ceil(stringer length ÷ maximum hole spacing) + 1, the standard method for laying out evenly-spaced connection points along a structural member
Inputs used
- Stringer Length
- 16.5 ft
- Maximum Hole Spacing
- 18 in
Intermediate steps
- Bays between holes
- 11
- Hole pitch, as drilled
- 1.5 ft
What this calculation does not cover
- The pitch above is the one to drill from, and it is not the maximum you typed: because the bays are rounded up, a 5 m (16 ft) stringer at a 0.45 m (1.5 ft) maximum is 12 bays at about 417 mm (16 in). What the pitch still assumes is that the run is the whole stringer, end to end — see the end distance below, which shortens it.
- The holes are spread across the whole length entered, which puts the first and last hole exactly on the two cut ends of the stringer. A bolt cannot sit on the end of a member: steel codes set a minimum end distance from the hole centre to the cut edge, normally expressed as a multiple of the bolt diameter or hole size, and the figure is jurisdictional. Set the end holes in by that distance and lay the remaining bays out over what is left.
- The layout is a single evenly-spaced line of holes along one gauge line. Staggered patterns and a second or third bolt row across the web or flange are outside it. For a detail with more than one row, multiply the count by the number of rows and check the cross-wise gauge separately.
- Drilling the holes removes material from a member that is usually working in bending, and this calculation says nothing about the stringer that is left. Net-section capacity along the drilled line and tear-out between adjacent holes are structural checks the count does not touch.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Bolt hole count = ceil(stringer length ÷ maximum hole spacing) + 1, the standard method for laying out evenly-spaced connection points along a structural member
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