Inside the App

The workflow at a glance

This image is from the current Construction Pro project and shows the product interface behind this guide.

Construction Pro rafter calculator with labeled roof geometry and cut-angle results. — Construction Pro on iPhone. Always verify field measurements and applicable building requirements.

Quick answer

Use half the building span as the run for a centered gable.
Enter pitch rise and horizontal run in Tools → Rafter Calculator.
Review rafter length and both cut angles before marking lumber.

Step by Step

Calculate Common Rafter Length and Cut Angles

Follow the sequence and keep units visible at every handoff.

Step 1

Confirm the roof geometry

For a centered gable, a 24-ft building has a 12-ft common-rafter run. Add overhang only where the tool requests it.

Step 2

Open the rafter tool

Go to Tools, choose Rafter Calculator, and select Common Rafter.

Step 3

Enter pitch and run

For a 6:12 roof, enter 6 as pitch rise and 12 ft as run. Keep ridge deductions separate from the geometric length.

Step 4

Review every output

The 12-ft run at 6:12 gives about 13 ft 5 in of geometric rafter length, a 26.57° plumb cut, and a 63.43° level cut. Verify the labeled diagram before cutting.

Field Examples

Three practical checks

Example 1

6:12 garage roof

A 12-ft run produces about 13.42 ft before construction-specific deductions.

Example 2

4:12 shed roof

A 10-ft run produces about 10.54 ft.

Example 3

Overhang check

Calculate the tail from the specified overhang workflow instead of silently adding it to building span.

Common mistakes

What to verify

Using full building width instead of half-span doubles the run.
Pitch 6:12 means 6 inches of rise per 12 inches of run, not six degrees.
Account for ridge thickness and field details before transferring the geometric result to lumber.

Related guides

Keep working

Can I use this result without checking it?

No. Confirm measurements, units, assumptions, and applicable code before cutting material, ordering supplies, or issuing a quote.

Does Construction Pro guess missing values?

No. Its calculators use explicit formulas and the inputs you provide; missing field conditions still require professional judgment.

Can I keep the calculation with a job?

Yes. Save verified calculations in a project and add a descriptive note so the crew can see what the result means.

Build Faster On Site

Take Construction Pro to the jobsite

Use feet-inch math, rafter tools, material estimates, and saved calculations from one construction calculator.

Download on the App Store