Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Roof angle (degrees)
26.57
Rafter length (ft)
16.99
Ridge rise (ft)
7.00
Roof pitch multiplier
1.1180
Slope (%)
50.0
Sloped area per ft of ridge
31.30
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter rise per 12 in run (in).
- 2Enter building span (ft).
- 3Enter overhang (in).
- 4Read your roof angle (degrees) on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Pitch is rise over a 12 in run. A 6/12 roof rises 6 in per foot, which is about 26.6 degrees and walkable for most roofers.
Worked example
Using the values the calculator loads with:
Inputs
- Rise per 12 in run: 6 in
- Building span: 28 ft
- Overhang: 16 in
Results
- Roof angle (degrees): 26.57
- Rafter length (ft): 16.99
- Ridge rise (ft): 7
- Roof pitch multiplier: 1.118
- Slope (%): 50
- Sloped area per ft of ridge: 31.3
What each field means
Inputs
- Rise per 12 in run (in)
- The rise per 12 in run used in the calculation, measured in in. Starts at 6 in so you have a working example on load. Accepted range: 0.5–24 in.
- Building span (ft)
- The building span used in the calculation, measured in ft. Starts at 28 ft so you have a working example on load.
- Overhang (in)
- The overhang used in the calculation, measured in in. Starts at 16 in so you have a working example on load.
Results
- Roof angle (degrees)
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Rafter length (ft)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Ridge rise (ft)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Roof pitch multiplier
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Slope (%)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Sloped area per ft of ridge
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the roof pitch, slope & rafter calculator work?
Pitch is rise over a 12 in run. A 6/12 roof rises 6 in per foot, which is about 26.6 degrees and walkable for most roofers. The underlying maths is: Angle = atan(rise ÷ 12); rafter = run × √(1 + (rise/12)²).
What do I need to enter?
3 values: rise per 12 in run, building span, and overhang. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the roof angle (degrees) result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Roof Pitch Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/roof-pitch
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/roof-pitch" target="_blank" rel="noopener">Roof Pitch Calculator — RevenueLab</a> (2026).</p>
Source: [Roof Pitch Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/roof-pitch) (2026).