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Stairs & stringers guide · 5 min read
How to measure a sloped stair rail
Carry stair rise and run into a usable sloped-rail length, then account separately for post insets and handrail extensions.
Start with the stair geometry
The sloped distance follows the hypotenuse created by the stair's total horizontal run and total rise. The Stair Calculator derives that base slope from the current riser and tread layout.
Stair slope length = √(total run² + total rise²)
Do not combine every length
- Post inset removes length from the guarded post-to-post zone.
- Handrail extensions add graspable length beyond the stair slope.
- Top and bottom rails usually terminate between posts and need their own joinery allowances.
- Stock ordering needs waste, joints and available lengths beyond the net calculated dimensions.
Field-measure installed connection points before fabrication. Framing position, post faces, brackets, returns and landing transitions can change the final cut lengths.