Calculadora de Escada
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
2·espelho + piso = 64 cm; projeção = nDegraus × piso
About this calculator
The Stair Calculator by UtilizAí is designed to help dimension residential stairs following Blondel's Rule. This ergonomic principle states that the sum of twice the riser height (2·r) plus the tread depth (t) should be between 63 and 65 cm. The ideal value is 64 cm, ensuring comfort and safety when going up and down. The calculator also determines the total horizontal projection of the stair by multiplying the number of steps by the tread depth.
How to use: enter the total height to be overcome (from lower to upper floor), the desired riser height (usually between 16 and 18 cm), and the tread depth (between 25 and 30 cm). The calculator checks if the combination complies with Blondel's Rule and displays the number of steps needed, the total projection, and the stair length. If the sum falls outside the range, an alert is shown suggesting adjustments.
When to use: ideal for residential projects, renovations, or new constructions where a comfortable and code-compliant stair is desired. Useful for architects, engineers, masons, and homeowners planning interior layouts. It also serves to verify existing designs or compare different step configurations.
Cautions: Blondel's Rule is an ergonomic guideline, but local building codes may require specific values or include additional requirements (such as handrails and minimum width). Always consult your municipality's building code. The calculator does not replace a complete structural design; for stairs over 3 meters in height or non-straight layouts, professional assistance is recommended.
Frequently asked questions
What is the ideal riser height for a residential stair?
The ideal is between 16 cm and 18 cm. Below 16 cm makes the stair too long, and above 18 cm can cause discomfort when climbing.
What if the sum 2·riser + tread is not between 63 and 65 cm?
Adjust the riser or tread. Reduce the riser and/or increase the tread, or vice versa, until the sum falls within the recommended range.
Does the calculator work for L-shaped or U-shaped stairs?
It calculates a straight flight. For stairs with landings or curves, dimension each straight section separately.
How many steps will my stair have?
Divide the total height by the chosen riser and round to the nearest whole number. The calculator does this automatically.
Do I need a handrail?
Yes, most codes require a handrail on at least one side for stairs with more than 3 steps. Check your local building code.