PFVPFV Tools
All tools

Staircase Calculator

Size a stair from the total rise — risers, treads, stringer length, and NBCC compliance.

  • staircase
  • stairs
  • riser
  • tread
  • stringer
  • rise
  • run
  • nbcc
  • building code

About Staircase Calculator

Laying out a flight of stairs is the kind of job where a small error compounds: get the riser height slightly wrong and it's multiplied across every step, leaving a final riser that's a trip hazard — and a building inspector's red flag. This calculator starts from the one measurement you can take reliably, the total floor-to-floor rise, and divides it into equal risers, then works out the matching tread run, the total horizontal run, and the stringer length you need to cut.

It also checks the result against the National Building Code of Canada (NBCC 9.8) limits for residential stairs and tells you, in plain terms, whether each dimension passes, needs a second look, or fails. A side-profile diagram shows the flight to scale so you can sanity-check the shape before you cut a single board.

How to use

Enter the total rise — the vertical distance from the lower finished floor to the upper finished floor — and your target riser height. The calculator rounds to a whole number of risers and shows the actual riser height that results, which is what you'll actually build to. Set the tread depth (the run of each step) and, optionally, the stair width to get tread-board material lengths.

The compliance banner checks riser height and tread run against the NBCC residential code ranges, plus the "2R + T" comfort guideline that trades use to judge whether a stair will feel right underfoot. Switch between metric and imperial at the top, and pick your jurisdiction so the advisory points you at the right building authority. Always confirm against your local code before building.

Frequently asked questions

  • How do I calculate the number of stairs I need?

    Divide the total floor-to-floor rise by your desired riser height and round to the nearest whole number — that's your riser count. Then divide the total rise by that whole number to get the actual riser height, which will be slightly different from your target. The number of treads is always one fewer than the number of risers, because the upper floor itself acts as the final step.

  • What is the building-code riser and tread limit in Canada?

    Under NBCC 9.8 for private residential stairs, risers must be between 125 mm and 200 mm, and the tread run must be between 235 mm and 355 mm. British Columbia, Ontario, and Quebec adopt the National Building Code with minor provincial variations, and commercial or public stairs have stricter limits — always verify with your local building department before building.

  • What is the "2R + T" rule?

    It's a long-standing rule of thumb for comfortable stairs: twice the riser height plus the tread depth (2 × riser + tread) should fall between roughly 550 mm and 700 mm. It captures the natural relationship between how high and how far each step takes you. A stair can meet the hard code limits yet still feel steep or stretched if it falls outside this band, which is why the tool flags it as a comfort warning rather than a failure.

  • How is stringer length calculated?

    The stringer is the diagonal board that carries the steps, so its length is the hypotenuse of a right triangle whose two sides are the total rise and the total run: stringer = √(rise² + run²). The figure shown is the straight cut length along the slope — add extra for the connection at the top and the footing or kicker at the bottom, which depend on how you're fixing the stair.

  • Why is the actual riser height different from the one I entered?

    Because the total rise rarely divides into a whole number of risers at exactly your target height. The calculator rounds to the nearest whole number of risers, then recomputes the riser height so every step is identical — equal risers are both a code requirement and essential for safety, since an odd step out is a common cause of falls. The value you enter is treated as a target, not a fixed figure.

More Construction tools