Door Header Size Calculator

A door header is the structural beam above a door opening that carries the weight of the wall and roof above it — choosing the wrong size can compromise a building's structural integrity. The Door Header Size Calculator lets you either find the recommended header size for a given opening or check the maximum span a specific header can handle. Enter your required clear span, load type, and lumber grade to get the recommended header size, maximum span, safety factor, and load capacity.

inches

Width of the door opening

Results

Recommended Header Size

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Maximum Span

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Safety Factor

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Load Capacity

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Results Table

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Frequently Asked Questions

How far can a 4x6 header span?

A 4x6 header can typically span up to 6 feet (72 inches) for standard residential loads. The exact span depends on the lumber grade, load conditions, and local building codes.

How do I calculate header size?

Header size is calculated based on the span length, load requirements, and lumber specifications. Generally, the header depth should be at least 1/12th of the span length for adequate structural support.

Can I use a 2x8 as a door header?

A single 2x8 is typically not sufficient for door headers in load-bearing walls. Most applications require doubled lumber (like two 2x8s) or engineered lumber for proper load support.

What size of header do I need for a 4-foot door?

For a 4-foot door opening, a 4x6 header is typically adequate for standard residential loads. However, always verify with local building codes and consider the specific load conditions.

Do all door openings need headers?

Headers are required for door openings in load-bearing walls. Non-load-bearing walls may not require structural headers, but check local building codes for specific requirements.

What's the difference between nominal and actual lumber sizes?

Nominal sizes are the traditional names (like 2x4), while actual sizes are smaller due to drying and planing. A nominal 4x8 header actually measures 3.5" x 7.25".

Can I use engineered lumber for headers?

Yes, engineered lumber like LVL (Laminated Veneer Lumber) or PSL (Parallel Strand Lumber) can often span longer distances than traditional lumber and may be more cost-effective for larger openings.