CalculatorAsphalt

Roof Pitch Calculator

Pitch ratio, angle in degrees and area multiplier from rise and run.

Quick answer: Pitch is rise per 12 in of run. Angle = arctan(rise/12); multiplier = √(1 + (rise/12)²). A 6:12 roof is 26.6° with a 1.118 area multiplier.

How to use this calculator

  1. Enter Rise in in.
  2. Enter Run in in.
  3. Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.

Formula & constants

Pitch is rise per 12 in of run. Angle = arctan(rise/12); multiplier = √(1 + (rise/12)²). A 6:12 roof is 26.6° with a 1.118 area multiplier. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.

Worked example. With rise = 10 in, run = 12 in, the calculator returns:
Pitch10:12
Angle39.8 °
Area multiplier1.302

Where this fits in the project

Roof takeoffs start from the footprint corrected by pitch: get true area from the roof square footage calculator, convert to squares, then to shingle bundles or metal panels. Size gutters from the same perimeter measurement.

How this connects to your project

No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the roof pitch calculator:

Frequently asked questions

How do I measure pitch on an existing roof?

Level held horizontal at the rake: measure 12 in along it, then vertical distance down to the roof — that’s rise per 12.

What pitch do shingles require?

Asphalt shingles need 2:12 minimum (with special underlayment 2–4:12); below that, use membrane roofing.

Last verified: — prices reflect current national averages. See our methodology.

Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.