Framing & Stairs Calculators

Framing and stairs are where geometry meets safety. The tools here work out board feet, roof pitch and stair dimensions, and the structural size of members and the legal limits on stairs come from the code.

Which tool answers which question

• Board Foot Calculator: Thickness, width and length to board feet and lumber cost.
• Roof Pitch Calculator: Rise and run to roof pitch, angle in degrees, slope percent, and rafter length.
• Stair Calculator: Total rise to riser height, tread count, stringer length and stair angle.

Board feet, pitch and stairs

A board foot is one inch thick by one foot square, so board feet equal thickness times width times length, divided by 12 when length is in feet. Roof pitch is the rise in inches for every 12 inches of horizontal run. Stairs need equal risers and equal treads, because uneven steps cause falls, and codes limit riser height and tread depth, so check your local limits before you cut stringers.

Common mistakes

• Uneven stair steps. A small difference causes trips and fails inspection.
• Using nominal sizes. A 2x4 is 1.5 by 3.5 inches.
• Guessing structural sizes. Use the code tables or an engineer.