Framing, roofing, and deck calculators

The stair calculator divides the total rise into equal risers at or under the maximum you set. The default maximum is IRC R311.7.5.1, 7¾ inches, and the tread check is R311.7.5.2, 10 inches. A flight that would rise more than 151 inches is flagged for a landing. Each extra flight adds a 36-inch straight landing to the run, from R311.7.6. The stringer length here is one flight. The woodworking stringer calculator cuts that flight, including nosing and throat.

Roof pitch is the same triangle as a rafter. Rise ÷ run × 12 is the pitch. Degrees are arctan of the slope. Percent is the slope times 100. The rafter multiplier is the hypotenuse of 1 and the slope, so a 6/12 is √1.25 = 1.118. Measure a rise and a run, or enter an angle, and the other three follow. The rafter calculator takes the rise-per-12 figure and a span.