Carpentry calculators & guides
Free carpentry tools and plain-English guides for United States — each gives the answer fast and shows the working behind it.
Board foot calculator
How many board feet do you have? Enter thickness, width, length and quantity — get the total board footage of lumber, plus the volume in cubic feet or metres.
Open tool →Drywall calculator
How much drywall do I need? Enter your room size and sheet size — get the number of sheets to buy, plus a screw estimate, for walls and ceilings.
Open tool →Plywood calculator
How many sheets of plywood do I need? Enter the area and pick your sheet size — get the sheet count instantly, with a waste allowance for cuts.
Open tool →Deck calculator
How many deck boards do I need? Enter the deck size, board and gap — get the boards, rows, lineal length and screws to order, with a waste allowance.
Open tool →Stair calculator
Enter your floor-to-floor rise — get the number of risers, riser height, run, stringer length and angle.
Open tool →Framing calculator
How many studs do I need? Enter the wall length, stud spacing, corners and openings — get the stud count plus the plate lumber for the wall.
Open tool →Joist & rafter span calculator
What is the maximum span of a 2x10 joist? Pick species, spacing and dead load — get the max span for common floor joists and roof rafters, per IRC span tables.
Open tool →About carpentry calculations
Carpentry layout is applied geometry. Stairs are the classic example: one measurement (the total rise from floor to floor) plus a couple of comfort targets generates the entire flight — riser height, tread count, total run, stringer length, and the angle of the saw cut. Framing, rafters and decking follow the same pattern: a few site measurements in, a full cut list out.
The carpentry tools here do that geometry instantly and show every intermediate step, so the number you carry to the saw is one you've seen derived, not one you're taking on faith. Long-standing layout rules of thumb (like the stair comfort rules) are clearly labelled as guidance, separate from any legal minimums.
Using the results
Measure twice, calculate once, and remember the calculator only knows what you typed: a total rise measured to subfloor instead of finished floor will be faithfully turned into a flight of stairs that's one flooring-thickness wrong. Check the calculated dimensions against the building rules enforced where you are — maximum riser heights and minimum tread depths are set locally, and they're enforced because stairs that break them genuinely cause falls.