Top Chord Length Calculator - Easily Estimate Your Roof Truss Chord

Last updated: 16 Jul 2025 | Author: Brij | Review By: Irshad

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Easily estimate the top chord length of a roof truss using span, pitch, overhang, and heel height.

Span (feet):

Pitch:

: slope

Overhang (inches):

Heel Height (inches):

Top Chord Calculation Results

Top Chord Length:

Top Chord Slope Angle:

Total Rafter Run:

Rise:

When building or designing a roof truss, one of the most important structural members is the top chord. It runs diagonally from the wall plate to the roof peak and supports the roof covering and loads above.

This Top Chord Length Calculator helps you determine the exact length of the top chord using inputs like span, roof pitch, overhang, and heel height. It's especially useful for architects, engineers, and DIY builders who want accurate rafter and truss calculations.

What Is the Top Chord?

The top chord is the sloped edge of a truss or rafter. Its length depends on how wide the building is (span), how steep the roof is (pitch), and any extra rise from heel height or horizontal run from overhang.

Formulas Used in the Calculator

Your code uses real-world geometry and trigonometry to determine the top chord length. Here's how each value is calculated:

1. Pitch Ratio

The slope of the roof is the rise over run. For example, 6:12 means 6 inches of rise per 12 inches of run.

$\text{Pitch Ratio} = \frac{\text{Pitch Rise}}{\text{Pitch Run}}$

2. Half Span

Since each top chord only covers half the total span:

$\text{Half Span} = \frac{\text{Span}}{2}$

3. Overhang (Converted to Feet)

$\text{Overhang (ft)} = \frac{\text{Overhang (in)}}{12}$

4. Total Run

$\text{Total Run} = \text{Half Span} + \text{Overhang (ft)}$

5. Rise (before heel height)

$\text{Rise} = \text{Total Run} \times \text{Pitch Ratio}$

6. Heel Height Adjustment

$\text{Total Rise} = \text{Rise} + \frac{\text{Heel Height (in)}}{12}$

7. Top Chord Length (Hypotenuse)

Using the Pythagorean theorem:

$\text{Top Chord Length} = \sqrt{(\text{Total Run})^2 + (\text{Total Rise})^2}$

8. Slope Angle (degrees)

To get the angle of the top chord from horizontal:

$\text{Slope Angle} = \tan^{-1}(\text{Pitch Ratio}) \times \frac{180}{\pi}$

Example Calculation

Let’s walk through an example using your calculator logic:

Inputs:

Span = 24 ft
Pitch = 6:12
Overhang = 18 inches
Heel Height = 6 inches

Step 1: Pitch Ratio

$\text{Pitch Ratio} = \frac{6}{12} = 0.5$

Step 2: Half Span

$\text{Half Span} = \frac{24}{2} = 12$

Step 3: Overhang in Feet

$\text{Overhang} = \frac{18}{12} = 1.5$

Step 4: Total Run

$\text{Total Run} = 12 + 1.5 = 13.5$

Step 5: Rise

$\text{Rise} = 13.5 \times 0.5 = 6.75$

Step 6: Add Heel Height

$\text{Total Rise} = 6.75 + \frac{6}{12} = 7.25$

Step 7: Top Chord Length

$\text{Chord Length} = \sqrt{13.5^2 + 7.25^2} = \sqrt{234.81} \approx 15.324$

Step 8: Slope Angle

$\text{Slope Angle} = \tan^{-1}(0.5) \times \frac{180}{\pi} \approx 26.57^\circ$

Final Output

Top Chord Length ≈ 15.324 ft
Total Rise = 7.25 ft
Total Run = 13.5 ft
Slope Angle ≈ 26.57°

Check out 1 similar Top Chord Length Calculator - Easily Estimate Your Roof Truss Chord :

Top Chord Length Calculator - Easily Estimate Your Roof Truss Chord

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