Professional Roof Slope Calculator

Comprehensive roofing calculator for contractors using verified geometric formulas

IMPORTANT DISCLAIMER: This tool provides estimates based on standard geometric formulas and industry averages. All calculations should be verified on-site by qualified professionals. Actual material requirements may vary based on specific job conditions, building codes, and manufacturer specifications.

Roofing Calculator

Limitations & Important Notes:
• Calculations assume standard rectangular buildings
• Waste factors are industry averages (adjust as needed)
• Complex roof features (valleys, dormers) require manual adjustment
• Always verify critical measurements on-site
• Consult local building codes for specific requirements

Calculate Pitch to Angle & Slope

Enter rise and run to calculate pitch ratio, angle, and slope.

Calculate Angle to Pitch

Enter roof angle to get pitch ratio and rise per 12 inches.

Calculate Rafter Length

Calculate rafter length from run and rise or span.

If you enter span, run will be calculated as span/2

Calculate Roof Area

Calculate roof area including pitch factor for different roof types.

Note: Hip roofs have same surface area as gable roofs. Extra waste for hip cuts is added in material estimation.

Material Estimation

Professional-grade estimates using verified industry formulas. For best results, enter building dimensions.

Required for accurate ridge cap and drip edge calculations

Industry waste factors: +12% for hip, +18% for complex roofs

Nail estimates: 2.5 lbs/sq (standard) vs 3.75 lbs/sq (high wind)

Calculation Results

Select a calculation type, enter values, and click "Calculate" to see results here.

Quick Pitch Reference

3:12 Pitch
Angle: 14.0°
Slope: 3 in 12
4:12 Pitch
Angle: 18.4°
Slope: 4 in 12
6:12 Pitch
Angle: 26.6°
Slope: 6 in 12
8:12 Pitch
Angle: 33.7°
Slope: 8 in 12

How to Use This Roof Slope Calculator

Step 1: Choose What You Want to Calculate

At the top there are 5 buttons. Each button is for different calculation.

  • Pitch to Angle - If you know rise and run, use this
  • Angle to Pitch - If you know roof angle, use this
  • Rafter Length - To calculate rafter length
  • Roof Area - To calculate roof area
  • Material Estimator - To estimate materials needed

Click on the button for what you want to calculate.

Step 2: Enter Your Numbers

After clicking button, you see boxes to enter numbers.

  • Rise - How high roof goes up (vertical)
  • Run - How far roof goes across (horizontal)
  • Angle - Roof angle in degrees
  • Length/Width - Building size
  • Pitch - Usually rise per 12 inches run

Put your numbers in the boxes. Use decimals if needed (like 6.5).

Step 3: Click Calculate Button

After entering numbers, click the big orange "Calculate" button.

The calculator will do all the math for you.

Step 4: Read Your Results

Results show on right side. You will see:

  • Pitch ratio (like 6:12)
  • Roof angle in degrees
  • Slope percentage
  • Rafter length if you calculated that
  • Roof area in square feet
  • Material estimates if you did that

Also see diagram that shows your roof shape.

Step 5: Print or Write Down Results

You can print the results page for your records.

Or write down the numbers for your roofing job.

Use these numbers for ordering materials, cutting rafters, etc.

Important Professional Notes:

  • Always verify critical measurements on-site
  • These are estimates - actual requirements may vary
  • Adjust waste factors based on job complexity
  • Consult local building codes for specific requirements
  • Complex roofs (valleys, dormers) need manual adjustment