Kerf Construction Calculator

Pay once — no subscription, ever. 20 trade calculators for concrete, stairs, roofing and pipe, each showing the formula and the code it cites. Offline. Yours for good.

Kerf Calc is the construction field calculator that just works — offline, no account, no subscription. Buy it once.

FEET-INCH-FRACTION, DONE RIGHT Punch dimensions the way you measure them: 8' 4-1/2" — add, subtract, multiply, divide, and read the exact result to your set fraction (1/8 to 1/64). Do real area and volume on the tape: 10' × 8' = 80 sq ft, × 4" = 26.67 cu ft.

EVERY TRADE, ONE APP • Framing — rafters (actual cut: line + overhang − ½ ridge, plus hip/valley/jack), stairs to IRC/IBC code with live riser/tread/headroom checks, right-angle & pitch • Concrete — slabs, footings, columns: yards, bags, ready-mix trucks, control joints, plus a waste allowance • Rebar — ASTM A615 sizes, weights, slab-mat, laps • Pipe — offsets (travel, run and the fitting multiplier at 45°, 22½°, 11¼° or any angle), rolling offsets, cut length from your own take-outs, and drainage grade in in/ft, percent, 1:N or degrees • Materials — roofing squares, drywall, paint, block, brick, mortar, pavers, board feet, compound miter • Convert — feet-inch ↔ decimal ↔ metric (NIST-exact)

ON YOUR WRIST The Apple Watch app carries all 20 calculators. Turn the Digital Crown to set a dimension and the answer is already on screen — rafter cuts on a roof, grade in a trench, bag counts at the pour. Runs on its own, with no phone and no signal.

SHOWS ITS WORK Every calculator shows the actual formula and the code or standard it cites (IRC, IPC/UPC, ASTM, NIST, ACI, NCMA, framing-square tables) — so you can trust the number, not just take it.

BUILT FOR THE JOB SITE Sunlight-readable light design, glove-sized keys, works with zero signal. iPhone, iPad, Apple Watch, and Mac.

Not certified engineering — a field calculator. Verify against your locally adopted code.