Roof Pitch Calculator

rise / run • x:12 • θ°
📈Rise
Tip: leave empty if you want to solve for rise.
📏Run length
Tip: leave empty if you want to solve for run.
🪚Rafter length
Computed from Pythagoras: rafter² = rise² + run².
⦿Roof pitch (°)
θ = arctan(rise/run).
％Roof pitch (%)
Percent = 100 × (rise/run).
🔢Roof pitch (x:12)
Common US format: rise per 12 units of run (e.g., 4:12).

⚡ Quick Summary

Enter any two compatible values (e.g., rise & run, or angle & run) and the rest will update automatically.

🧩 Step-by-step derivation

  1. We compute slope p = rise/run from what you entered (angle, %, or x:12).
  2. Then find missing lengths using rafter² = rise² + run² and trigonometry.
  3. All units convert instantly when you change a unit selector.

📚 References

TopicKey formula / noteSource
Roof slope formatsAngle (°), percent, and x:12 ratioWikipedia – Roof pitch
Right triangle relationrafter² = rise² + run²Any standard geometry / trigonometry text