Stair Formula

Overarching term for the calculation rules for comfortable stairs.

Stair formulae comprise the three classical rules for calculating a comfortable step ratio: the step-ratio formula (2R + G ≈ 63 cm), the safety formula (R + G ≈ 46 cm) and the comfort formula (G − R ≈ 12 cm). The step-ratio formula is the most common and forms the basis of DIN 18065. All three are based on the average human stride length and help to plan stairs that are safe and pleasant to use.