Handrail Length Calculator

About this calculator

A sloped stair handrail's total length isn't just the horizontal run or vertical rise — it's the hypotenuse along the slope, found with the Pythagorean relationship √(run² + rise²), plus any horizontal extensions required at the top and bottom landings for code compliance and graspability. This calculator computes that sloped length, adds your specified top and bottom extensions, and reports the slope angle (arctan of rise over run) that the rail — and its wall brackets — will need to be cut and mounted at.

Stair builders, finish carpenters and code inspectors use this calculation because most building codes (like the IRC in the US) require handrail extensions of roughly one tread depth at the top and bottom of a stair run, specifically so a hand can find secure support before the first step and after the last one — getting the sloped length and angle right the first time avoids re-cutting an expensive hardwood or metal rail, since the cut angle at each end must match the slope precisely to seat flush against the newel post or wall bracket.