Carpentry calculators

Assumes the top floor acts as the last tread, so treads = risers − 1. Stringer length is the straight line along the nose line from the bottom to the top; add material for the end cuts and the notch. No code limits are built in: type the limits that apply where you build. The "2R + T" check is only the traditional rule of thumb (commonly quoted as about 600 to 640 mm, or 24 to 25 in); the two fields above are editable and switch to inches when you switch units (enter 24 and 25).

Common rafter = √(run² + rise²), measured along the top edge from the plate line to the ridge line. Results are in the unit you typed the run in. Hip/valley figures assume two equal-pitch roof planes meeting at 90 degrees in plan (hip run = run × √2). Ridge thickness, birdsmouth and tail cuts are not deducted.

1 board foot = 144 cubic inches = 0.0023597 m³. Enter the actual size you will buy or the nominal size your supplier prices by (a nominal 2×4 is about 1.5 × 3.5 in, which is 3.5 board feet at 8 ft; priced by nominal size it is counted as 5.33).

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Accepts mixed numbers (3 1/2 or 3-1/2), fractions, decimals, feet and inches (5' 3 1/2"), and mm or cm suffixes. Results are rounded to the nearest fraction you pick, so a long chain of calculations should be done on the exact figures and rounded only at the end.

First-fit decreasing: pieces are sorted longest first and each goes on the first board with room, counting one kerf per cut. It is fast and usually good but not guaranteed to be the minimum number of boards. Allow for end defects and for squaring the board ends yourself.