About Jobsite Calculator

Jobsite Calculator is a small set of free carpentry and framing calculators for DIYers and contractors. Everything runs in your browser: no signup, no accounts, nothing stored.

Methodology

Stair results start from total rise, the only measurement that cannot be adjusted on site. We divide it by a target riser height, round to the nearest whole number of risers, and divide again so every riser is identical. Tread count is one less than the riser count for a flight that finishes flush with the upper floor, and total run is tread count multiplied by tread depth. Stringer length is the hypotenuse of total rise and total run; the angle is the arctangent of riser over tread.

Code references

• IRC R311.7.5.1 — maximum riser height 7 3/4 in.
• IRC R311.7.5.2 — minimum tread depth 10 in.
• IRC R311.7.5 — maximum 3/8 in. variation between the largest and smallest riser.
• IRC R311.7.2 — minimum headroom 6 ft 8 in.
• Rule of thumb: 2 × riser + tread should land between 24 in. and 25 in.

Disclaimer

Results are for planning only. Local amendments differ, so confirm dimensions with your building inspector before cutting material.