Steel · Members & beams

Stair stringer calculator

Inclined stringer carrying half the stair: horizontal-span moment, shear, and deflection along the incline.

Standard: AS 4100 · AS/NZS 1170.1 stair loads

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Result	Value	Unit
Inclined length	5.00	m
Line load per stringer 1.2G + 1.5Q (plan)	4.46	kN/m
M* = w Lh²/8	8.93	kNm
V*	8.93	kN
Service load perpendicular to stringer per incline length	2.00	kN/m
Deflection 5 w Li⁴/(384 EI)	4.28	mm
Limit Li/limit	13.89	mm

Diagram for the worked example

Inclined length = SQRT(4^2+3^2) = 5 m
Line load per stringer 1.2G + 1.5Q (plan) = (1.2*1.2+1.5*4)*1.2/2 = 4.464 kN/m
M* = w Lh²/8 = 4.464*4^2/8 = 8.928 kNm
V* = 4.464*4/2 = 8.928 kN
Service load perpendicular to stringer per incline length = (1.2+4)*1.2/2*(4/5)^2 = 1.9968 kN/m
Deflection 5 w Li⁴/(384 EI) = 5*1.9968*(5*1000)^4/(384*200000*1.900e+7) = 4.2763 mm
Limit Li/limit = 5*1000/360 = 13.889 mm

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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.