Kā izmantot Rafter Length Calculator — calculate rafter length from roof pitch
Estimate common-rafter slope length from horizontal run, roof pitch and the required overhang.
Slope length over the structural run = run ÷ cos(pitch). The configured overhang is then added along the slope.
Estimate common-rafter slope length from horizontal run, roof pitch and the required overhang. The linked Sellible tool keeps the fields, units and output together so the assumptions can be reviewed before the result is used.
- 1
Establish the true horizontal run.
- 2
Enter the pitch in degrees and slope overhang.
- 3
Use the result for planning stock length, not as a cutting schedule.
Example values and result
These values demonstrate the method; replace them with measurements, rates or file details that match the real task.
- Horizontal run
- 4.0 m
- Roof pitch
- 30°
- Slope length before overhang
- about 4.62 m
- Overhang along slope
- 0.30 m
The example gives approximately 4.92 m before practical cutting details. Birdsmouths, ridge details and support geometry need separate setting out.
Precizitāte un praktiski norādījumi
- Confirm ridge thickness and support reference points.
- Account for plumb cuts, birdsmouths and tails.
- Follow structural drawings and timber grading requirements.
Common mistakes
- Adding horizontal overhang as though it were slope length.
- Ignoring the ridge and wall-plate geometry.
- Treating a length estimate as structural design.
A free account makes repeat tasks simpler
Email-link sign-in keeps file jobs, downloads, support and usage available across devices. Browser calculators remain free.
Biežākie jautājumi
Is Rafter Length Calculator free?
Yes. This calculator or browser utility is free and does not use processing credits.
Can I use this guide and Rafter Length Calculator on a phone?
Yes. The guide, inputs, results and calls to action are responsive and keyboard accessible on current phones, tablets and desktop browsers.
Should I order or make a decision from the estimate alone?
No. Confirm ridge thickness and support reference points. Account for plumb cuts, birdsmouths and tails. The calculation is a planning aid rather than professional or regulatory approval.
How should I check the result?
Keep the source values and units visible, compare the result with supplier or project information, and retain enough precision until the final purchasing or reporting step.