Why Proper Header Sizing Matters

Headers transfer weight from above to the jack studs and foundation, preventing sagging and structural failure. Undersized headers can lead to:

Doors/windows that won't open properly
Cracks in drywall and finishes
Structural instability in extreme cases

Calculation Guide

Our calculator uses the standard formula: Header Size = (Opening Width × Load Factor) ÷ 2

Measure the rough opening width between jack studs
Select the appropriate load type for your application
The result shows the minimum required header depth in inches

Standard Header Sizes Reference

Opening Width	Minimum Header Depth
Up to 3'	3.5" (2×4)
3'-6'	5.5" (2×6)
6'-8'	7.25" (2×8)
8'-10'	9.25" (2×10)

Important Considerations

⚠️ Always consult local building codes

These calculations provide general guidance only. Local codes, snow loads, and special conditions may require engineering approval.

Frequently Asked Questions

What happens if I use an undersized header?

Undersized headers can sag over time, causing doors and windows to stick, cracks in drywall, and in extreme cases, structural instability.

Can I double up headers for wider openings?

Yes, doubling headers (using two pieces) is common practice for wider openings. The calculator results already account for standard doubled header construction.

Do I need special headers for exterior walls?

Exterior walls typically require larger headers due to additional load considerations. Always use the "Heavy Load" option for exterior openings.

Header Size Calculator for Doors and Windows

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Header Size Calculator for Doors and Windows

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