Building & Carpentry calculators
Framing, envelope, and site calculators for builders and carpenters. Structural results are planning estimates, not engineered designs.
- Arc Radius CalculatorFor a chord c and rise h, the radius is c² ÷ (8h) + h ÷ 2, and the arc length is the radius times the included angle in radians.Inputs: Chord length, Rise
- Concrete Block Wall CalculatorA standard 8×16 in block covers 128 square inches of wall, so a wall needs 1.125 blocks per square foot, less openings, plus waste.Inputs: Wall length, Wall height, Openings
- Concrete Slab and Footing CalculatorConcrete volume is length × width × thickness; divide cubic feet by 27 for cubic yards, and add a waste allowance before you order.Inputs: Length, Width, Thickness or depth
- Hip and Valley Rafter Length CalculatorHip or valley rafter length = common run × √(2 + (rise ÷ 12)²), for two equal-pitch roof planes meeting at a right angle.Inputs: Roof pitch: rise per 12 in of run, Common run, Jack rafter spacing
- Rafter Length and Birdsmouth Cut CalculatorCommon rafter length = run × √(1 + (rise ÷ 12)²), and a birdsmouth notch may not exceed one-fourth of the rafter depth under the IRC.Inputs: Roof pitch: rise per 12 in of run, Building span, Overhang
- Rebar Grid CalculatorBars per direction = (dimension − 2 × cover) ÷ spacing + 1, and total weight equals total length times the bar’s nominal weight per foot.Inputs: Slab length, Slab width, Bar spacing
- Retaining Wall Block and Gravel CalculatorBlocks needed = courses × (wall length ÷ block length), where courses = exposed height ÷ block height plus the buried base courses, with waste added.Inputs: Wall length, Exposed wall height, Block face length
- Roof Snow Load CalculatorFlat roof snow load pf = 0.7 × Ce × Ct × Is × pg, and a sloped roof load is that value times the slope factor Cs.Inputs: Ground snow load pg, Exposure factor Ce, Thermal factor Ct
- Roofing Squares and Shingle Bundles CalculatorRoof area equals the footprint (with overhangs) times a pitch factor of √(1 + (rise ÷ 12)²); divide by 100 for squares, and buy 3 bundles per square.Inputs: Building length, Building width, Overhang on each side
- Stair Stringer CalculatorDivide the total rise by your preferred riser height to get the number of steps, then use that many equal risers with treads at least 10 inches deep.Inputs: Total rise, Preferred riser height, Tread depth
- Wall Framing Stud Count CalculatorStuds equal the wall length ÷ spacing, rounded up, plus one, plus extra studs at each corner and opening; add three lengths of plate for a double top plate.Inputs: Wall length, Wall height, Stud spacing
- Wall R-Value CalculatorA wall's effective R-value is lower than its insulation R-value because studs carry heat around the cavity; the parallel path method combines both paths.Inputs: Exterior finish, R-value, Continuous insulation or insulating sheathing, R-value, Building paper / air barrier, R-value