roof calculator
Roof Pitch Calculator (Metric)
The metric Roof Pitch Calculator uses millimetres, centimetres, metres, or square metres as shown beside each field. It applies angle = arctan(rise ÷ run), places a complete metric result in the served HTML, and updates locally in the browser. Verify field measurements, local standards, material data, and structural assumptions before construction.
Calculated result
22.62°
Roof angle = arctangent of rise divided by run.
- Pitch
- 5.00/12
- Slope factor
- 1.0833
- Percent grade
- 41.7%
Printable result and cut list
| Item | Value | Job note |
|---|---|---|
| Primary result | 22.62° | Verify before cutting or ordering. |
| Pitch | 5.00/12 | Calculated from the entered dimensions. |
| Slope factor | 1.0833 | Calculated from the entered dimensions. |
| Percent grade | 41.7% | Calculated from the entered dimensions. |
| Formula | Expression | Note |
|---|---|---|
| Primary formula | angle = arctan(rise ÷ run) | Round the final result, not each intermediate value. |
How the roof pitch calculation works
Enter the job dimensions in the form. The calculator normalizes the values, applies angle = arctan(rise ÷ run), and updates the main result, supporting values, diagram labels, and print table together.
The first displayed example is calculated during the static build. That makes the formula and a complete numerical result readable in page source, while the browser script handles later input changes.
Worked example
The prefilled values form a complete roof angle and slope factor example. Change one field at a time and compare the updated result with the formula table to catch unit or transcription mistakes.
Common errors to avoid
- Mixing nominal and actual material dimensions.
- Entering diameter where the formula expects radius, or total run where it expects one tread.
- Rounding every intermediate value instead of rounding the final purchase or cut quantity.
- Treating a planning result as a stamped structural design or local-code approval.
Guide cluster
Roof Pitch guides
Roof Pitch: How to Measure the Inputs
Roof Pitch: How to Measure the Inputs with a practical sequence for measurement order, datum selection, and unit consistency, a worked calculation, and links to the live tool and printable chart.
Roof Pitch: Formula and Worked Example
Roof Pitch: Formula and Worked Example with a practical sequence for formula order, intermediate values, and final rounding, a worked calculation, and links to the live tool and printable chart.
Roof Pitch: Common Mistakes to Avoid
Roof Pitch: Common Mistakes to Avoid with a practical sequence for input mix-ups, premature rounding, and field-condition errors, a worked calculation, and links to the live tool and printable chart.
Roof Pitch: Material Planning Guide
Roof Pitch: Material Planning Guide with a practical sequence for net quantity, waste, stock sizes, and purchase rounding, a worked calculation, and links to the live tool and printable chart.
Roof Pitch: Code and Safety Checks
Roof Pitch: Code and Safety Checks with a practical sequence for source boundaries, local rules, and professional verification, a worked calculation, and links to the live tool and printable chart.
Roof Pitch: Printable Job-Sheet Workflow
Roof Pitch: Printable Job-Sheet Workflow with a practical sequence for record keeping, revision control, and field handoff, a worked calculation, and links to the live tool and printable chart.
Frequently asked questions
Does the roof pitch calculator work without JavaScript?
The default worked result, formula, diagram, and result table are included in the served HTML. JavaScript is only needed to recalculate after you change an input.
Which unit should I use?
Use the imperial page for US customary inputs or open the metric twin for millimetres, centimetres, and metres.
Can I use the result for purchasing material?
Use it as a quantity and layout check, then add the stated waste allowance and confirm package coverage, stock dimensions, and field conditions.
Does this replace building code or an engineer?
No. The calculator is a planning aid. Current local code, product documentation, and a qualified engineer govern structural and life-safety decisions.
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iPhone companion
Keep jobsite math available offline
The website calculators and charts stay free. The BuildMath iPhone app keeps its supported construction calculations available when the jobsite has no connection.
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