Total rise in, full stringer layout out: riser count and height, tread run, angles, and the board to buy — sized to the common code limits, printable for the sawhorses.
finished floor to finished floor / deck surface
per step, nose to riser (10″ minimum)
Set stair gauges on a framing square to your riser height and tread run, hook the square over the 2×12’s edge, and walk it down the board tracing each step. Cut the lines with a circular saw, stopping at the inside corners, and finish every corner with a handsaw — overcutting weakens the stringer at exactly the wrong spot. Drop the bottom riser by one tread’s thickness so the first step matches the rest once treads go on.
The International Residential Code — the base for most US local codes — caps risers at 7¾″ and requires treads at least 10″ deep, with no more than ⅜″ variation between the tallest and shortest riser in a flight. Local amendments differ (some jurisdictions allow 8¼″ risers), so verify the numbers with your local building department before cutting.
It divides your total rise by the 7¾″ maximum and rounds up — the fewest risers that keep each one legal — then splits the rise evenly so every step is identical. Identical risers matter more than the exact height: a ⅜″ surprise in the middle of a flight is what trips people.
The top surface — deck or floor — acts as the final tread. A flight with 7 risers has 6 treads cut into the stringer. If your stringer instead tucks under the deck so the deck is not a step, add one tread and say so to your inspector.
Cut stringers from 2×12s: after notching, the narrowest remaining section (the throat) should stay at least 5″, which a 2×12 gives with code-size steps. The calculator reports the stringer’s tip-to-tip length — buy the next standard length up and cut the plumb and level cuts from that.
The old carpenter’s check: twice the riser plus the tread should land between 24″ and 25″. A 7¼″ riser with a 10½″ tread gives 25″ — right in the pocket. The calculator flags combinations that fall outside it.
An occasional email when a new calculator ships. No spam, easy out.
Parts list in, cutting layout out — sheet goods or boards, with kerf, grain locks, waste %, and a printable diagram.
Thickness × width × length → board feet and cost, with the 4/4–8/4 quarters convention explained inline.
Screw gauge + hardwood or softwood → pilot, clearance, and countersink bit sizes from one chart.