Stair Calculator

Laying out a staircase

Comfortable, code-compliant stairs come down to two measurements: the riser (the height of each step) and the tread (its depth). This calculator takes your total floor-to-floor rise, divides it into evenly sized risers, and reports the actual riser height and total horizontal run.

Code and comfort

• Risers are typically capped at 7¾″ in residential code; 7″ is comfortable.
• Treads are usually at least 10″ deep.
• The Blondel rule — 2 × riser + tread should land near 24–25″ — is the classic comfort check the tool runs for you.

FAQ

Why is there one fewer tread than risers?

The top riser lands on the upper floor itself, so a flight always has one more riser than it has treads. That's why the total run is the tread depth times (risers − 1). Always confirm against your local building code before cutting stringers.

What is the Blondel rule?

It's a classic comfort formula: two times the riser height plus the tread depth should land near 24–25 inches. The calculator runs this check for you so the steps feel natural to climb rather than too steep or too shallow.

What are typical riser and tread limits?

In residential construction risers are usually capped around 7¾ inches, with about 7 inches feeling comfortable, and treads are typically at least 10 inches deep. Exact limits vary by jurisdiction, so always verify against your local building code.

Why do I get an odd riser height like 7.43 inches?

The total rise rarely divides into a round number of equal steps, so the tool finds the riser count that keeps each step within a comfortable, code-friendly range and reports the exact resulting height. Every riser must be the same to be safe.

Is the calculator free, and does it work on mobile?

Yes to both. It is free with no sign-up, runs in your browser so your measurements stay private, and works in any phone browser so you can use it on site. Treat the results as a planning estimate and confirm against local code.