Roof Rafter Length Table: Rafter length by Horizontal run
Reference table of rafter length for Roof Rafter Length across a range of horizontal run values — exact, engine-computed figures you can read off at a glance.
Roof Rafter Length Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Rafter length
4.772
- Sloped length (no overhang)
- 4.472
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Roof Rafter Length Calculator
The Roof Rafter Length Calculator works out your rafter length, along with 1 related figure in an instant. Enter horizontal run, vertical rise and overhang and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the horizontal run.
- Enter the vertical rise.
- Enter the overhang.
- Read off your rafter length, together with sloped length (no overhang) — the calculator updates automatically, with no button to press.
Formula
The Roof Rafter Length Calculator uses the formula:
Rafter length = √(Horizontal run ^ 2 + Vertical rise ^ 2) + Overhang
Worked example
For example, with horizontal run of 4 m, vertical rise of 2 m and overhang of 0.3 m, the rafter length is 4.772.
| Horizontal run | 4 m |
|---|---|
| Vertical rise | 2 m |
| Overhang | 0.3 m |
| Rafter length | 4.772 |
|---|---|
| Sloped length (no overhang) | 4.472 |
Results are estimates for educational use, not professional advice.
Frequently asked questions
Use the Pythagorean theorem on run and rise, then add the overhang. A 4 m run with 2 m rise gives about 4.47 m, plus overhang.
Run is the horizontal distance from wall to ridge; rise is the vertical height the roof climbs over that run.
The rafter extends past the wall to form the eaves, so the overhang is added to the sloped length.
It gives the rafter line length. Allow extra for plumb cuts, the ridge board and the birdsmouth notch.
The Roof Rafter Length Calculator uses the formula: Rafter length = √(Horizontal run ^ 2 + Vertical rise ^ 2) + Overhang. For example, with horizontal run of 4 m, vertical rise of 2 m and overhang of 0.3 m, the rafter length is 4.772.
Enter the horizontal run. Enter the vertical rise. Enter the overhang. Read off your rafter length, together with sloped length (no overhang) — the calculator updates automatically, with no button to press.
Related guides
How to Calculate Roof Rafter Length: Formula, Steps & Examples
Learn how to calculate Roof Rafter Length — the formula explained step by step, with worked examples and a free calculator to check your answer.