Header Size Calculator

About this calculator

A header (or lintel) is the horizontal structural member above a door or window opening that carries the load from the wall and roof above down to the studs on either side. The wider the opening's clear span, the bigger — and often the more layered — the header lumber needs to be, and load-bearing walls need larger headers than non-load-bearing partition walls for the same span.

This calculator takes your opening's span in feet and the load type (bearing or non-bearing) and estimates a recommended header size, such as a doubled 2×8 or 2×10, based on standard residential framing span tables. It's a starting reference for DIY builders and framers planning a new opening or widening an existing one — always meant to be checked against local building code and, for structural work, an engineer's sign-off.