Door Header Size Calculator

Finding the right header size for a door or window doesn’t have to feel like rocket science. That’s exactly why we built the Door Header Size Calculator. It gives you quick results with simple math and saves you from flipping through long building charts. Let’s break it down step by step.

Why header size matters

Headers act like mini beams above your doors and windows. They carry the weight of the wall or roof above. Use one that’s too small, and you risk sagging or even failure. Use one that’s too big, and you’ll waste money and space. That’s where our calculator steps in it finds the sweet spot in seconds.

The simple formula behind the calculator

There’s a neat little rule for header spans. It goes like this:

Maximum span (in inches) = Header depth (in inches) × 12

For example, if you use a 6-inch deep header, the maximum span is:

6 × 12 = 72 inches, or 6 feet.

So if your doorway is 5 feet wide, a 4" × 6" header will do the trick.

How to use the Door Header Size Calculator

Using the tool is easy. You’ll have two options:

Find the right header size

1. Enter your rough opening (doorway width including frame).
2. Select the unit of measurement (inches, feet, cm, or meters).
3. The calculator shows you the recommended header size.

Find the maximum span for a header

1. Choose your header size (like 4" × 10").
2. The calculator displays the maximum span that header can carry.
3. You’ll also see the result in different units feet, cm, and meters.

That’s it. No confusing steps. Just type in the numbers and get instant answers.

Common header size examples

What size header for a 14 foot span?

You’ll need a 4" × 14" header since 14 × 12 = 168 inches, or 14 feet.

How do I know what size headers I need?

Measure the rough opening, divide by 12, and round up to the next standard size.

What size beam do I need for a 16 ft span?

For a 16-foot span, the formula gives 16 inches of depth. That means a 4" × 16" header.

What size header for a 10 foot span?

A 4" × 10" header covers a 120-inch (10-foot) span.

Final verdict

The Door Header Size Calculator is like having a carpenter’s cheat sheet in your pocket. It’s fast, accurate, and takes the guesswork out of framing. Whether you’re planning a new build, remodeling, or just curious, you’ll find it simple and reliable.

FAQs

Can I use a 2x8 as a door header?

Yes, but you’ll need to double it up with a spacer to make it match standard 4-inch thickness.

How far can a 4x6 header span?

It can span up to 6 feet or 72 inches.

Do I need to add extra length for studs?

Yes, cut your header about 3 inches longer to fit jack studs on both sides.

Does this work for windows too?

Absolutely. The same formula applies since windows and doors need the same support.