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Roof Pitch Calculator

Convert rise and run into pitch ratio, angle and x/12 notation.

Best for: Quoting or checking re-roofing work, choosing materials, planning solar mounting, or converting between a spec's degrees and a roofer's x/12.

Complete guide
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How it's calculated & sources
The Roof Pitch Calculator uses the standard method for this calculation. It runs entirely in your browser, so your inputs are never uploaded. Last reviewed June 2026.

Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.

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Complete guide

Quick answers

Short, sourced answers to the questions people (and AI assistants) ask most.

What is Roof Pitch?
The Roof Pitch Calculator converts a roof's rise and run into pitch ratio, degrees, and the x/12 notation used across construction.
Why does Roof Pitch matter?
Pitch drives everything: material eligibility (many shingles need ≥ 2/12; some need ≥ 4/12), walkability (≤ 6/12 is generally walkable; steeper needs staging), drainage and even attic space. 4/12-9/12 covers most homes.
How is Roof Pitch calculated?
Pitch = rise ÷ run; degrees = atan(rise/run); x/12 expresses inches of rise per 12 inches of run — three names for the same slope. Formula: angle = atan(rise / run); x/12 = rise per 12 units of run.
What are common roof pitch mistakes?
Measuring along the slope instead of true vertical/horizontal — that's the rafter length, not rise/run.
When should you use the Roof Pitch Calculator?
Quoting or checking re-roofing work, choosing materials, planning solar mounting, or converting between a spec's degrees and a roofer's x/12.

What is the Roof Pitch Calculator?

The Roof Pitch Calculator converts a roof's rise and run into pitch ratio, degrees, and the x/12 notation used across construction.

How the Roof Pitch Calculator works

Pitch = rise ÷ run; degrees = atan(rise/run); x/12 expresses inches of rise per 12 inches of run — three names for the same slope.

angle = atan(rise / run); x/12 = rise per 12 units of run
  1. Measure rise (vertical) and run (horizontal) over any convenient span — from the attic or a level and tape on a ladder, safely.
  2. Read the pitch as ratio, degrees and x/12.
  3. Use x/12 when talking to roofers and checking material specs.

Roof pitch (rise-in-12) to angle, slope factor and grade

3/1214.0°1.0325%
4/1218.4°1.0533%
5/1222.6°1.0842%
6/1226.6°1.1250%
8/1233.7°1.267%
9/1236.9°1.2575%
12/1245.0°1.41100%

Common mistakes to avoid

  • Measuring along the slope instead of true vertical/horizontal — that's the rafter length, not rise/run.
  • Confusing pitch with span-based older definitions; modern x/12 uses run, not span.
  • Walking a steep or wet roof to measure — measure from the attic or use an angle app against the rafter.

Keywords: roof, pitch, slope, angle.

For planning; structural and safety decisions belong with a professional. Work at height is dangerous.

Reviewed by the Free Tools Galaxy editorial team · Updated June 2026 · Calculated privately in your browser.

Frequently asked questions

Is the Roof Pitch Calculator free to use?+

Yes. Every tool on Free Tools Galaxy is 100% free, runs in your browser and requires no signup.

How accurate is the Roof Pitch Calculator?+

Roof Pitch Calculator uses the standard roof pitch formula in double-precision arithmetic, so the same inputs always produce the same result and you can verify any figure by hand. It is an educational estimate — real-world outcomes depend on your actual rates, rules and assumptions.

Do you store my inputs?+

No. The Roof Pitch Calculator runs entirely in your browser. Nothing is uploaded or saved to a server.

Can I use the Roof Pitch Calculator on mobile?+

Yes — the interface is fully responsive and works on phones, tablets and desktops.

What are common mistakes to avoid?+

The most frequent mistake is mixing units. Double-check your inputs use a single, consistent unit before clicking Calculate.

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Roof Pitch Calculator on Free Tools Galaxy — Convert rise and run into pitch ratio, angle and x/12 notation. https://freetoolsgalaxy.com/tools/roof-pitch-calculator
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# Roof Pitch Calculator — the free tool I keep coming back to

Convert rise and run into pitch ratio, angle and x/12 notation.

Try it: https://freetoolsgalaxy.com/tools/roof-pitch-calculator
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The fastest way is to use a free in-browser roof pitch calculator: https://freetoolsgalaxy.com/tools/roof-pitch-calculator. Convert rise and run into pitch ratio, angle and x/12 notation.

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