Staircase calculator
Risers, treads, going, pitch and comfort check from floor-to-floor height.
How it is calculated
Number of risers = floor-to-floor height ÷ maximum riser, rounded up. Riser = height ÷ number of risers. A straight flight has one tread fewer than risers. Total going = treads × tread depth. Pitch = arctan(riser ÷ tread). Comfort (Blondel): 2 × riser + tread should be between 550 and 700 mm (about 22–27½ in).
Check locally: Maximum riser, minimum tread, pitch, headroom and handrail rules differ by country and building type. Check the code that applies to your project.
How to use the Staircase Calculator
Design a comfortable stair from the floor-to-floor height: the number of risers, riser height, treads, total going and pitch, with a section drawing and a comfort check.
- Enter the floor-to-floor height (finished floor to finished floor).
- Enter the maximum riser your building code allows and the tread (going) you want.
- Choose a straight stair, a straight stair with a mid landing, or a dog-leg with a half landing, and set the landing depth.
- Check the pitch and the 2R + T comfort range, and adjust the tread until both are comfortable.
Worked example
For a 3 m floor-to-floor height and a 175 mm maximum riser, you need 18 risers of 166.7 mm. With 275 mm treads, a dog-leg stair has two flights of 9 risers and 8 treads each, a pitch of 31.2° and 2R + T of 608 mm, inside the comfortable 550 to 700 mm range.
Good to know
- Every riser in a flight should be the same height. The calculator always rounds the riser count up so no riser exceeds your maximum.
- A straight flight has one tread fewer than it has risers, because the top step is the floor above.
- Codes also set headroom, handrail and landing rules; check the one that applies to your project.
Questions
What is the 2R + T rule?
Twice the riser plus the tread (going) should be between about 550 and 700 mm for a comfortable stair. It is a guide, not a code requirement.
Does it check building codes?
No. It shows the geometry. Maximum riser, minimum tread and headroom rules depend on your country and building type.
Is anything I enter saved or sent?
No. The calculation runs in your browser. Nothing you type is sent anywhere. You can copy the result, print it or download it as a CSV.