Roof Truss Calculator
Calculate the number of roof trusses needed for a building based on roof length, truss spacing, and overhang. Also estimates total cost.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Roof Truss Calculator
This calculator determines the number of roof trusses needed and the total cost based on your roof dimensions and truss spacing.
- Enter Roof Length (ft) – Input the total length of the roof in feet (e.g., 40).
- Enter Truss Spacing (ft) – The distance between each truss center (default is 2 ft). Must be greater than 0.
- Enter Overhang (ft) – The roof overhang on each side (default is 0). Can be 0 or positive.
- Enter Cost per Truss ($) – Optional cost per truss to calculate total cost (default is 0).
- Click Calculate or press Enter in any input field.
- Number of Trusses = ceil((Roof Length + 2 × Overhang) / Truss Spacing) + 1
- Total Cost = Number of Trusses × Cost per Truss
Results:
All inputs are in feet (imperial). Ensure values are positive numbers. The calculator will show an error if inputs are invalid.
Previous Results
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Frequently Asked Questions
Measure the horizontal distance from one end of the roof to the other, excluding overhangs. The calculator adds overhang automatically.
Common spacings are 2 ft or 24 inches on center for residential roofs. Commercial may use 4 ft or more. Always consult local building codes.
Yes, the formula includes an extra truss for the gable end. The result is the total number of trusses needed for the entire roof length.