Calculators

Free construction calculators

The calculations that cost real money when they are done wrong or done late. Every one runs entirely in your browser — no account, no upload, and nothing you type reaches us.

Roof pitch & common rafter

Pitch to angle, slope factor, and common rafter length with the ridge deduction and tail.

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Stair stringer layout

Equal risers from a total rise, with tread depth, total run, stringer length and the 2R+T check.

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Board feet

Board feet from nominal dimensions, for one piece or a whole order.

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Concrete volume

Slabs, continuous footings and round piers in cubic yards, with waste and bag counts.

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Hip & valley rafter

Hip length, hip angle, and the common difference that steps every jack rafter down.

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Compound miter for crown

Miter and bevel settings for sprung moulding cut flat, at any spring and corner angle.

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Conduit offset bending

Multiplier, distance between bends, and the shrink to take off the measurement.

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Pipe rolling offset

True offset, travel and run when a pipe moves up and sideways at once.

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Rebar mat & weight

Bar count both ways, total linear feet and weight, for a slab mat at your spacing.

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Wall framing takeoff

Studs, plates and sheathing for a straight wall — with what is deliberately left out.

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Roofing squares & bundles

Footprint and pitch to roof area, squares and bundles, with waste.

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Drainage slope & fall

Total fall over a run, in inches per foot, percent or ratio — all three at once.

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Why these are free

Because they are the same arithmetic the app does, and there is no good reason to put a signup between a framer and a rafter length. If they save you a trip back to the truck, Keld on your phone will save you more — it works offline, where the signal usually is not.

Reference tables

The lookups that go with them: