Get the header framing right: how many jack studs, how much bearing, when a flat 2×4 is allowed, and when you need an engineered beam. Then read your exact header size from IRC Table R602.7 for your conditions.

Opening span (ft)

Wall type

Header supports (load-bearing)

Jack Studs Per End

— per end

Trimmers supporting each end of the header.

Usage Tip

Build headers from members on edge, not laid flat — on-edge is far stiffer. In a 2×6 wall, fill between paired members with 1/2 in. plywood so the header is full wall thickness. Verify your size against IRC Table R602.7 and local code.

THE MATH

Jack studs per end = 1 if span ≤ 6 ft, otherwise 2
Bearing per end ≥ 1.5″
Engineered beam if span > about 10 ft or under a point load

Span is the clear width of the rough opening. Jack studs (trimmers) carry the header reaction down to the plate; king studs run full height beside them.
The header size itself comes from IRC Table R602.7 by building width, ground snow load, and what the wall supports — this tool does not replace that lookup.

This tool applies the consistent framing rules from IRC R602.7: jack-stud count, end bearing, the non-bearing exception, and when an engineered beam is needed. It deliberately does not output a lumber size, because the size depends on building width, snow load, species, and floors supported that vary by project.
Read the paired-2x size from Table R602.7 for your exact conditions, or use an LVL span table from the beam supplier.
Confirm with your local building department, and use a structural engineer for point loads, long spans, or anything outside the prescriptive table.