Stair Flight Calculator

A flight is an unbroken run of risers between two landings — the ground floor, an intermediate landing, or the upper floor. A straight run from basement to main floor with no break is one flight, even if it has 15 steps.

As soon as you introduce a landing partway up, whether to turn a corner or just to break up a tall rise, you now have two flights joined by that landing.

Commonly cited IRC reference values limit a single flight to a maximum vertical rise of 12 ft 7 in between landings for residential stairs. IBC reference values for most stairs commonly cite a similar 12 ft limit.

These numbers vary by jurisdiction, and the local authority having jurisdiction has final say, but as a planning rule of thumb: if your total floor-to-floor rise is pushing past 12 ft, plan on a landing.

Beyond the hard rise limit, long uninterrupted flights are simply harder to climb and harder to fall safely on. Many designers add a landing well before hitting a code maximum, especially for stairs used by children or older adults.

A landing also gives you a place to turn the stair 90° or 180°, which is often the real reason people search for flight calculators — not the rise limit itself, but fitting a tall stair into a shorter footprint by turning it.

Once you decide on two flights, divide the total riser count as evenly as possible. If the total doesn't split evenly, put the extra riser in the lower flight — it's a minor convention, not a hard rule, but it keeps the upper flight (often more visible) at the rounder number.

1. Calculate total risers for the full rise, as you would for a single flight.
2. Divide the riser count by 2 and round each half to a whole number.
3. Assign the odd extra riser (if any) to the lower flight.
4. Recalculate actual riser height for each flight separately — they should be nearly identical, ideally matching exactly.
5. Size the landing at a minimum of 36 in in the direction of travel, more if the stair turns there.

A quick reference for when a single flight is fine and when to plan a landing.

Commonly cited reference values call for a landing at least as wide and as deep as the stair itself, with a minimum of 36 in in the direction of travel. If the stair turns at the landing, the landing usually needs to be sized to the full width of both flights combined.

Don't shortchange landing depth to save floor space — a landing that's too shallow undermines the whole point of breaking up a long flight.

If the landing is there for a turn rather than just breaking up rise, look at the L-shaped stair calculator or U-shaped stair calculator, which handle the geometry of the turn itself alongside the flight split.