From this site

One project, every trade

Each calculator adds its lines to a single estimate — consolidated BOM, schedule and cash-flow included.

Open My Project →

Roof Pitch to Degrees Calculator

Convert an American rise-over-12 roof pitch into degrees for cutting, setting out and metric drawings.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Roof angle

26.57 °

High confidence

Angle = arctan(rise ÷ 12), which is exact rather than approximate. Set a mitre saw to the complement of this angle for plumb cuts — a 26.57° roof takes a 63.43° setting on some saw scales.

American roofing is specified as a ratio — 4:12, 6:12, 12:12 — while saws, pitch gauges and every metric drawing want degrees, so anyone cutting rafters from a US drawing crosses this boundary constantly. The conversion is an exact arctangent, and a handful of reference points are worth memorising: 4:12 is 18.43°, 6:12 is 26.57°, and 12:12 is exactly 45°. Two practical cautions. First, the run in the ratio is horizontal, so a tape laid along the rafter measures the slope length and yields a flatter figure than the true pitch. Second, saw scales differ: some read the angle from the blade's plumb position rather than from horizontal, so a 26.57° roof may need 63.43° dialled in. Cut one test piece against the actual rafter before committing to a stack of them.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Roof pitch expressed as rise per 12 units of run; angle = arctan(rise / 12)
  • Common reference points: 4:12 = 18.43°, 6:12 = 26.57°, 12:12 = 45°

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Why does my saw need a different number than this?
Some mitre saw scales read from the blade in its plumb position rather than from horizontal, so they want the complement — 63.43° for a 26.57° roof. Others read directly. Cut one offcut and offer it up to the rafter before running the whole stack.
What angle is a 12:12 roof?
Exactly 45°, because the rise equals the run. It is the one pitch you can check without a calculator, and a useful sanity test that you have entered rise rather than rafter length.
Does the pitch change the material quantity?
Yes. A steeper roof has more surface area over the same footprint, and that is handled by a pitch multiplier rather than by this conversion. Convert the angle here, then apply the multiplier to your plan area before ordering covering.