NEC · IRC · ACI references
Jobsite math you can scale, print, and take to the yard.
SiteSpecCalc runs four deterministic calculators in the browser. Change a dimension and the blueprint, the bill of materials, and the side-by-side comparison move with it. Imperial units cover feet, inches, cubic yards, pounds, and AWG. Metric covers meters, millimeters, cubic meters, kilograms, and square millimeters.
Slab, rebar, and bags
Cubic yards, cubic meters, 60 lb and 80 lb bags, rebar sticks, chairs, and a scaled grid.
Wire size and voltage drop
AWG and mm² for copper or aluminum, with end voltage, percent drop, and I²R loss.
Stair stringer layout
Equal risers to the sixteenth, total run, 2x12 length, and an IRC pass or warning.
Roof pitch and rafters
Pitch angle, rafter length, plumb and seat cuts, squares, bundles, and sheathing.
Same formula every time
Volumes, voltage drop, riser counts, and rafter lengths are TypeScript functions. Nothing on a click calls a language model. The optional OpenAI script is an offline seed tool for new pages, not part of the calculator.
Code limits, labeled
Stair pages flag risers outside 4 to 7.75 inches and treads under 10 inches. Wire pages color the drop at 3 and 5 percent. Slab pages cite the IRC minimum thickness and keep PSI as a specification you price yourself.
4 engines, 40 presets
Each preset opens the matching calculator with its own dimensions, a comparison table, engineering notes, and FAQ schema. Freight pages reuse those engines for truck loads, pallets, and spool weight.
Preset jobs
40 indexable calculator pages with the inputs already filled.
Concrete & Masonry
20×20 Garage Slab: 4 Inch vs 6 Inch
A 20 ft square garage pad at 4 in, with the comparison table repeating the takeoff at 6 in.
Concrete & Masonry
10×12 Shed Pad: Bags vs Ready-Mix
A small 10 by 12 ft shed pad where bagged concrete often beats the short-load fee.
Concrete & Masonry
24×30 Monolithic Shop Slab with Rebar
A 24 by 30 ft monolithic shop slab with a thickened edge and a 16 in rebar grid.
Concrete & Masonry
6×6 Hot Tub Pad, 6 Inch Reinforced
A small 6 ft square, 6 in pad with a tight rebar grid for a hot tub.
Concrete & Masonry
12×40 Concrete Driveway Thickness and Cost
A 12 by 40 ft driveway apron priced at 5 in, with 4 in and 6 in beside it.
Concrete & Masonry
30×40 Barn Slab at 6 Inches and 4,000 PSI
A 30 by 40 ft agricultural slab at 6 in with a 16 by 12 in turned-down edge.
Concrete & Masonry
16×16 Patio Slab at 4 Inches
A square 16 ft patio with a light #3 mat and low waste.
Concrete & Masonry
12×24 Carport Slab, 5 Inch, 18 Inch Grid
A single-bay carport pad, 5 in thick, with an 18 in rebar grid.
Concrete & Masonry
8×10 Generator Pad, 8 Inch, 5,000 PSI
A heavy 8 in equipment pad for a generator, with a #5 mat.
Concrete & Masonry
40×60 Monolithic Shop Slab with Turn-Down Footing
A large 40 by 60 ft monolithic slab with an 18 in deep turned-down edge.
Electrical, EV & Solar
50 Amp EV Charger Wire Size at 50, 75, and 100 Feet
A continuous 50 A, 240 V charger. The table repeats 50, 75, and 100 ft runs.
Electrical, EV & Solar
100 Amp Subpanel Feeder: Copper vs Aluminum
A 100 A, 240 V feeder at 80 ft, with copper and aluminum side by side.
Electrical, EV & Solar
30 Amp RV Outlet Wire Gauge and Voltage Drop
A 120 V, 30 A TT-30 style outlet where voltage drop shows up quickly.
Electrical, EV & Solar
200 Amp Main Service Entrance Wire Size
A 200 A service lateral where ampacity, not voltage drop, usually governs.
Electrical, EV & Solar
240 V Mini-Split Heat Pump Wire Gauge
A 25 A heat pump on 240 V, 60 ft from the panel, with the 125 percent ampacity check on.
Electrical, EV & Solar
60 Amp Detached Garage Subpanel Wire Size
An 80 ft feeder to a detached garage subpanel at 60 A.
Electrical, EV & Solar
20 Amp Well Pump Wire Size at 150 Feet
A long 150 ft well branch where drop, not the 20 A breaker, picks the wire.
Electrical, EV & Solar
15 Amp Lighting Run Voltage Drop at 100 Feet
A 100 ft, 120 V lighting circuit at 15 A and a 3 percent limit.
Electrical, EV & Solar
40 Amp Electric Range Wire Size at 40 Feet
A short 40 ft, 40 A range circuit where ampacity usually wins.
Electrical, EV & Solar
480 V Three-Phase 100 Amp Shop Feeder
A 100 A, 480 V, three-phase feeder, 120 ft, copper in EMT.
Structural Framing & Wood
Deck Stair Stringer Calculator, 36 to 96 Inch Rise
A 72 in deck rise as the working case, compared with 36 through 96 in.
Structural Framing & Wood
Basement Stair Stringer for a 9 Foot Floor-to-Floor Rise
A 9 ft 0 in floor-to-floor basement stair. Add joist depth if your ceiling is 9 ft and the floors are farther apart.
Structural Framing & Wood
6/12 Roof Pitch, Rafter Length, and Shingle Bundles
A 6/12 gable, 24 ft wide and 40 ft long, with a 12 in overhang.
Structural Framing & Wood
4/12 vs 8/12 Gable Roof Material Estimator
The same 28 by 40 ft gable priced at 4/12, with 8/12 in the comparison table.
Structural Framing & Wood
Interior Stair, 108 Inch Rise, 10 Inch Tread
An interior stair at the IRC minimum tread and a 108 in rise.
Structural Framing & Wood
Deck Stairs, 48 Inch Rise, Three-Stringer Layout
A low deck, 48 in to grade, hung with a dropped header.
Structural Framing & Wood
12/12 Pitch Gable Rafter on a 24 Foot Span
A 12/12 gable. The plumb cut and the seat cut are both 45 degrees.
Structural Framing & Wood
Shed Roof 3/12 Pitch on a 10 by 12 Foot Building
A small shed roof. The full 10 ft width is the run, not half of it.
Structural Framing & Wood
9/12 Pitch Roof on a 30 Foot Span
A steeper 9/12 house roof with a longer eave overhang.
Structural Framing & Wood
Porch Stairs, 24 Inch Rise, IRC Riser Check
A short porch flight. Three risers at 8 in would fail, so the equal-riser math matters.
Freight & Logistics
Ready-Mix Truck Loads for a 20×30 Slab
Freight view of a 20 by 30 ft slab: yards per 10 yard truck and order weight.
Freight & Logistics
Pallet Count for 80 lb Bags on a 12×16 Pad
A bagged-concrete delivery: pallets, bag count, and pounds on the truck.
Freight & Logistics
Rebar Bundle Weight for a 24×24 Slab Grid
A tight 12 in grid so the rebar weight, not the concrete, is the delivery question.
Freight & Logistics
Shingle Bundle Delivery Weight for a 6/12 Roof
Roofing freight: bundles at 70 lb, sheets at 46 lb, and underlayment rolls at 28 lb.
Freight & Logistics
2×12 Stringer Lumber Haul for a 108 Inch Stair
Lumber delivery for the 9 ft floor-to-floor stringers.
Freight & Logistics
Copper Wire Spool Weight for a 100 Amp, 150 Foot Feeder
A long copper feeder where the spool weight matters as much as the gauge.
Freight & Logistics
Aluminum Feeder Freight for a 200 Amp Service Lateral
Service-lateral freight: large aluminum conductors, short run, high weight per foot.
Freight & Logistics
Plywood Sheathing Delivery for a 30×40 Gable
A sheathing haul: sheet count, waste, and pounds for a 30 by 40 ft, 6/12 roof.
Freight & Logistics
Hot Tub Pad Short-Load Concrete Delivery Fee
A very small pour where the short-load fee can exceed the concrete.
Freight & Logistics
12×40 Driveway: Ready-Mix vs Bagged Delivery
The 12 by 40 ft driveway again, this time as a haul choice between a truck and pallets.