Construction calculators — what are you calculating today?
Pick the job, get the number. Every tool reads and answers in feet-inch-fractions — type 12' 6 1/2" the way you'd say it, not decimal soup. Free, no sign-up, built by the crew behind the Stairkey Takeoff Builder.
Stairs & framing
Cut a walkable stair, lay out rafters, and nail the angles.
Stair Calculator
Enter the total rise and get a uniform, walkable stair: riser height and count, tread depth, total run, stringer length, and incline — in feet and inches, free.
Rafter Calculator
Span and pitch to common rafter length, plumb and seat cut angles, birdsmouth HAP and ridge height, rafter count, lumber footage, and roof area in squares
Crown Miter Calculator
Spring angle and corner angle to the miter and bevel settings for crown molding — flat or nested, inside or outside corner, single- or dual-bevel saw, with left- and right-piece cut direction. Free.
Slope Calculator
Run and rate to total fall, ramp length, and the same slope in inches-per-foot, percent, and degrees — plus the fall needed to hit a drainage target. Free.
Concrete & site work
Pour the slab, fill the base — order the right volume.
Finishes & materials
Figure out how much to buy before the supply run.
Drywall Calculator
Room dimensions or square footage to sheet count for 4×8, 4×9, 4×10, or 4×12 board — doors and windows deducted, waste applied, plus screws, joint compound, and tape. Free.
Paint Calculator
Room dimensions to wall area and gallons, with doors, windows, coats, and coverage accounted for.
Flooring Calculator
Multiple rooms or runs to total square footage, waste allowance, and box count — add areas, subtract cutouts,
Board Feet Calculator
Nominal size, length, and quantity to board feet and cost — with the nominal-vs-actual rule handled correctly. Free.
Layout & geometry
Space it evenly, prove it square, work the shape.
Spacing Calculator
On-center stud and joist counts with the last bay, equal-gap baluster and picket layout, and fence post counts to a max span
Square-Up Calculator
Length × width to the diagonal that proves square, an out-of-square verdict from your measured diagonal, and 3-4-5 corner marking
Circle & Arc Calculator
Circumference and area, arc length and chord, ring borders — and the field trick: measure a chord and rise to find the radius of an existing curve. Free.
Polygon Calculator
Octagon decks, gazebos, bay windows: side count plus one measurement gives the corner miter, side length, perimeter, and area
Planning tools — results are estimates for quoting and ordering, not engineering or building-code advice.