Door Header Size
Free door header size calculator — find the recommended header for any rough opening or check the max span of standard lumber headers from 4x4 to 4x12.
About This Calculator
A door header (also called a door lintel or door beam) is a horizontal structural member installed above a door opening to transfer the weight of the wall and roof above it to the jack studs on either side. Choosing the correct header size is essential for structural safety and building code compliance in residential and light commercial construction.
Our door header size calculator uses the industry-standard rule: the maximum span of a wood header equals the nominal depth of the lumber in inches multiplied by 12 (L = d x 12). A 4x4 header spans up to 48 inches, a 4x6 spans up to 72 inches, a 4x8 spans up to 96 inches, a 4x10 spans up to 120 inches, and a 4x12 spans up to 144 inches. To find the recommended header for a given rough opening, divide the opening width in inches by 12 and round up to the nearest even whole number to get the required depth. The standard header width is 4 inches to match a 2x4 wall frame.
This calculator offers two modes: Find Recommended Header Size — enter your rough opening width and get the correct header size; and Find Max Span for a Header — select a standard header size to see its maximum allowable span. Results are displayed in both inches and feet for convenience.
Regional Notes
United States: The rule-of-thumb method (depth x 12) is widely accepted for standard residential construction and aligns with International Residential Code (IRC) guidelines. Always verify against your local building department's requirements. Typical header lumber is Douglas fir-larch, SPF, or hem-fir graded No. 2 or better.
United Kingdom: Door headers are typically referred to as lintels and are commonly made from pre-stressed concrete or steel. Concrete lintels are sized based on span and load calculations following BS EN 1995 (Eurocode 5). Consult a structural engineer for non-standard openings.
India: RCC (Reinforced Cement Concrete) lintels are the standard for door openings in masonry construction. Steel or wood headers are less common. Sizing follows IS 456:2000 guidelines. Always consult a structural engineer for load-bearing walls.
Frequently Asked Questions
How do I determine the correct door header size?
To determine the correct door header size, measure the rough opening width of your doorway and divide by 12. Round up to the nearest even whole number to get the required header depth in inches. A 4-inch depth header (4x4) spans up to 48 inches, a 6-inch depth (4x6) spans up to 72 inches, and so on. The header width is typically 4 inches to match a standard 2x4 wall frame.
What size header do I need for a 6-foot door?
For a 6-foot (72-inch) rough opening, you need a 4x6 door header. The rule is: header depth in inches times 12 equals maximum span in inches. A 6-inch deep header spans up to 72 inches, making it the correct choice for a 6-foot door opening.
What size header do I need for a 4-foot door?
For a 4-foot (48-inch) rough opening, a 4x4 door header is sufficient. A 4-inch deep header spans up to 48 inches. Cut the header to the rough opening width plus 3 inches to accommodate the thickness of the jack studs on each side.
Can I use a 2x8 as a door header?
Yes, you can use 2x8 lumber as part of a door header, but you need to build up a 4x8 beam by gluing two pieces together on their wider side with a half-inch spacer between them. A single 2x8 does not provide sufficient thickness for a standard wall header — the finished header should be approximately 3.5 inches thick to match a 2x4 wall.
How far can a 4x12 header span?
A 4x12 header can span up to 144 inches or 12 feet. This is calculated using the formula: header depth (12 inches) times 12 equals 144 inches. The 4x12 is the largest standard header size and is used for the widest door and window openings in residential construction.
What is the formula for calculating door header size?
The formula for door header sizing is L = d x 12, where L is the maximum rough opening span in inches and d is the nominal depth of the lumber in inches. To find the required header size for a given opening, divide the rough opening width in inches by 12 and round up to the nearest even number to get the required depth. The standard header width is 4 inches for 2x4 wall construction.
What is a rough opening for a door?
A rough opening is the framed opening in a wall where a door and its frame will be installed. It is typically 2 to 3 inches wider and taller than the actual door size. For example, a 36-inch wide door requires a rough opening of approximately 38 to 39 inches. The rough opening width is used to determine the required door header size.
Do I need a structural engineer to size a door header?
For standard residential door openings up to 6 feet wide, the rule-of-thumb method (depth times 12) is widely accepted and does not require a structural engineer. However, for openings wider than 6 feet, load-bearing walls, or non-standard construction, you should consult a structural engineer or local building department to verify header sizing meets your area's building codes.