Roof Pitch Calculator | Calculate Slope, Angle & Rise

Unit System

Quick Presets

Presets set pitch as rise in 12 (Imperial). In Metric, presets convert to mm rise per 1 m run.

Rise (in)

Vertical increase.

Run (in)

Horizontal distance (default 12 in or 1 m if blank).

Pitch (rise in 12)

Rise for every 12 in (or per 1 m metric).

Angle (°)

Slope (%)

Precision

Half-span (ft)

Wall plate to ridge (horizontal). Required to show rafter length.

Overhang/Eave (ft)

Horizontal add-on to rafter (used only if half-span is provided).

Roof Length (ft)

Ridge length. With span, used for roof area.

Building Span (ft)

Total width (wall to wall). With roof length, used for roof area.

Roof Triangle (to scale)

Diagram is illustrative based on your current rise/run. Not for code-compliance drawings.

Roof Pitch Calculator – Angle, Slope, Rafter Length & Area

This roof pitch calculator converts between pitch (rise in 12), angle in degrees, and slope percentage. Enter any one (or both rise and run) and the tool solves the rest. For estimating, enter your half-span and optional overhang to calculate a common rafter length. If you provide roof length and building span, it also estimates roof surface area for quoting underlayment, shingles, or metal sheets.

What Does Roof Pitch Mean?

In Imperial units, pitch is written as X-in-12 (e.g., 6/12 means the roof rises 6 inches for every 12 inches of run). In Metric, this calculator treats pitch as mm rise per 1 meter of run for consistency.

Typical Roof Pitches

Low slope: 2/12–4/12 (≈9.5°–18.4°)
Common residential: 4/12–8/12 (≈18.4°–33.7°)
Steep slope: 9/12+ (≈36.9°+)

How We Calculate

Angle (°) = arctan(rise/run)
Slope (%) = (rise/run) × 100
Common rafter length uses half-span as the horizontal run; overhang extends the horizontal run and rise proportionally.
Roof surface area = (roof length × building span) ÷ cos(angle) for simple gable roofs

Related Roofing Calculators

Roof Square Footage Calculator Roof Truss Calculator Shingle Calculator

FAQs

Is pitch the same as angle?
No. Pitch is a ratio (e.g., 6/12). Angle is the arctangent of rise/run in degrees. The calculator shows both.

What do I enter for run?
If you’re working from a pitch like 6/12, you can leave run blank; the calculator assumes 12 inches (or 1 m in Metric) as the reference run.

How accurate is the area?
It’s an estimate for simple gable roofs. Complex roofs (hips/valleys/dormers) require component-by-component takeoffs.

Accuracy & Review

Reviewed by: Caleb Wright

Caleb validates our roofing calculators, reviewing shingle coverage assumptions, waste factor guidance, and ventilation recommendations. He focuses on practical jobsite accuracy to help ensure estimates reflect real-world installation conditions.

Last updated: Feb 12, 2026

See: Methodology · Data Sources · Review Board

Important Estimate Disclaimer

Results are preliminary estimates only and do not replace professional roofing specifications. Material quantities may vary based on pitch complexity, waste factors, underlayment layers, and local code requirements.

Review our Methodology and Data Sources for calculation details.

Wind exposure, flashing requirements, and structural considerations may affect final material totals.