Load Bearing Wall Header Size Calculator

Calculator

Clear opening span, L (ft)

Tributary width (ft)

Dead load (psf)

Live load (psf)

Roof or snow load (psf)

Center point load, P (lb)

Header self weight (plf)

Available bearing length (in)

Header material

Load duration factor

Deflection limit

Reset

Example Data Table

Example	Span	Tributary width	Dead load	Live load	Point load	Planning note
Interior door opening	3 ft	4 ft	10 psf	40 psf	0 lb	Often controlled by practical depth.
Wide room opening	6 ft	8 ft	12 psf	40 psf	0 lb	Deflection may control the choice.
Opening below post	5 ft	6 ft	10 psf	40 psf	1200 lb	Point loads raise moment and reaction.
Roof bearing wall	8 ft	10 ft	15 psf	20 psf	0 lb	Snow load and local rules matter.

Formula Used

The calculator treats the header as a simply supported beam. It combines uniform area load and an optional center point load.

Area load = dead load + live load + roof or snow load.
Line load, w = area load × tributary width + self weight.
Total load = wL + P.
Support reaction, R = (wL + P) / 2.
Maximum moment, M = wL² / 8 + PL / 4.
Required section modulus, S = M / adjusted bending stress.
Deflection = 5wL⁴ / 384EI + PL³ / 48EI.
Shear stress for rectangular sections = 1.5V / bd.
Required bearing length = reaction / compression bearing capacity.

How To Use This Calculator

Enter the clear opening span in feet.
Enter tributary width from framing supported by the header.
Add dead, live, roof, or snow service loads.
Add a center point load when a post lands above.
Select the material, duration factor, and deflection limit.
Press the calculate button and read the result above the form.
Download the CSV or PDF report for planning records.
Review the result with local code officials or a qualified professional.

Why Header Size Matters

A wall opening changes how loads move through a building. Studs once carried weight straight down. A header redirects that weight around the opening. It sends force into jack studs at each side. Correct sizing helps limit sag, cracks, sticking doors, and stress. This calculator gives a planning estimate. It is not a permit design.

Loads Behind The Opening

A header may carry ceiling load, floor load, roof load, snow load, and wall weight. The tributary width estimates how much surface area feeds the beam. Larger tributary width creates a larger line load. A concentrated load can represent a post above the opening. The tool combines these values into one service load.

Strength And Stiffness Checks

The calculation checks bending first. Bending controls many longer spans. Shear is also checked near supports. Deflection is checked because a safe member can still bend too much. Bearing at the jack stud is checked as well. A strong beam still needs enough support area.

Choosing A Practical Header

The smallest passing member is not always the best field choice. Builders may choose a deeper member for stiffness. They may choose more plies to match wall thickness. Moisture, notches, fasteners, and holes can reduce capacity. Engineered members can carry more load, but they need approved installation details.

Use Results Carefully

This page is useful for early planning, comparison, and material conversations. It helps you see which input affects the answer most. Increase span and the required section rises quickly. Increase tributary width and every strength check becomes harder. Local codes, species grades, bearing paths, and inspection rules still control the final header. Always keep final design approval with a qualified professional.

Input Quality Matters

Better input gives better output. Measure the opening, not the rough frame guess. Use service loads that match the actual story above. Separate roof load from floor load when possible. Add point loads only when a post, girder, or stacked support truly lands above the header.

When To Ask For Design Help

Ask for design help when removing wide walls, supporting masonry, changing multiple stories, or working near damaged framing. Older buildings may hide unusual load paths. Renovations can also change support conditions during field work.

FAQs

Is this result approved for construction?

No. It is a planning estimate. Final header sizing depends on code rules, plans, material certificates, connections, bearing path, and site conditions.

What is tributary width?

Tributary width is the supported floor, ceiling, or roof width feeding load into the header. Larger width creates higher line load.

Why does point load matter?

A post or concentrated beam reaction above an opening can increase bending and support reaction. Add it when that load lands near midspan.

Why check deflection?

A member can be strong enough but still bend too much. Deflection checks help reduce drywall cracks, trim gaps, and sticking openings.

Does this include notches or holes?

No. Notches, holes, damage, moisture, poor fastening, and eccentric loads need separate review. They can reduce useful strength.

Can I use it for masonry walls?

Do not rely on it for masonry, concrete, or steel lintels. Those systems need different checks, bearing rules, and detailing.

What if no option passes?

Use a deeper member, add plies, reduce the span, reduce tributary load, add posts, or request engineered design help.

Why is bearing length included?

The header must transfer reaction into jack studs without crushing support fibers. More reaction often needs more bearing area.