Stair Calculator

Divide the total rise by your maximum riser height and round up to get the riser count, split the rise into equal risers, multiply the treads by your tread depth for the total run, and solve the diagonal for stringer length.

Stair Calculator

Method and assumptions

Figur turns your measurements into purchase quantities with standard geometry: it computes the area, length, or volume, applies the waste or spacing you enter, and rounds up to whole purchase units. Everything is calculated locally in your browser.

Purchase quantities round up to whole units (sheets, bundles, boards, bars, or packages) because suppliers do not sell fractions.
Assumed coverages and package sizes (for example, 3 bundles per square or 4×8 sheets) are common conventions; verify your product label and supplier.
The waste percentage is applied exactly as entered; complex cuts, patterns, and damage can require more.
The result does not replace your field measurements, plans, or local code requirements.

This tool provides a planning takeoff, not a binding bid, structural design, or engineering advice. Confirm quantities with field measurements, your supplier, and the applicable professionals before buying.

Sources and references

No external data source is required: this calculator applies standard geometry to the measurements, coverages, and waste you enter.

Frequently asked questions

Why 7.75 inches as the default maximum riser?

Many residential codes based on the IRC cap risers at 7 3/4 inches and require steps in a flight to be nearly equal. Always confirm the limits your local code actually enforces before cutting stringers.

Is the stringer length the board length to buy?

The result is the geometric diagonal of the stair. Buy stock longer than that number so you can lay out the cuts, and remember stringers lose strength at the deepest notch.