About

FramingCalcs publishes free calculators for roof geometry, framing layout and material takeoff. Every tool shows the geometry or standard practice behind its answer, so you can check the reasoning rather than trusting a number.

We build these because the arithmetic is rarely the hard part. A rafter calculator that returns the hypotenuse leaves out ridge shortening, so every rafter comes out long. A hip rafter cut on a twelve inch unit run rather than sixteen and ninety-seven hundredths comes out badly short. A deck board count that divides by six rather than five and a half runs nine percent short, and it is discovered with two rows left to lay.

Where the numbers come from

Most of it is geometry, and geometry can be checked: right-triangle trigonometry for rafters, hips and pitch, the compound angle formulas behind a crown moulding cut, the moment arithmetic that turns a span into a tributary load. Our published dimensional data is verified against its own definition — the nominal-versus-actual lumber rule, sheet areas, the AWG and circular mil standards — rather than transcribed and hoped over.

Where a published standard governs, it is cited by section: IRC R806.2 for attic ventilation ratios, R905.2 for the slope thresholds that decide what a roof can be covered with, and the USDA Wood Handbook coefficients behind seasonal wood movement.

What we deliberately do not publish

There are no joist, beam, header or rafter span calculators here, and no stair, guard, footing or snow load tools either. Their absence is a decision rather than an oversight.

Each of those depends on a code table — IRC span tables covering species and grade, presumptive soil bearing values, riser and tread limits, ASCE 7 snow factors — where one wrong cell produces a confident, authoritative answer that is structurally unsafe, and no amount of software testing catches a table that is wrong in a consistent way.

They will be published when those tables have been checked against a verified current code copy. Until then, use the tables in your code book, or an engineered design. A calculator that looks authoritative and is wrong about a beam or a stair is worse than no calculator at all.

What these tools are not

They are estimates for planning and material takeoff. They are not engineered designs or permit documents, they do not determine whether a wall is load bearing, and they do not size the members that carry load. Local amendments to the IRC are common and your building department has the final say. Every calculator carries a disclaimer naming what it does not model.