How to Choose the Right Screw Length for Your Woodworking Project

Choosing the right screw isn’t just about the drive type or gauge — length matters too.

Use a screw that’s too short and you may not get enough holding power. Go too long and you risk the screw coming through the other side of your timber.

At Screw it Screws, we specialise in Robertson® square-drive screws, so here are a few simple tips to help you choose the right screw length for your next woodworking project.

A Simple Rule for Choosing Screw Length

As a general starting point, you want enough of the screw to penetrate well into the second piece of timber without coming through the other side.

For many woodworking applications, having roughly two-thirds of the screw length entering the material being fixed into can provide a useful starting point.

However, there isn't one perfect rule for every project. Timber thickness, screw gauge, load, timber species and whether the joint is structural can all affect the right choice.

Check the Thickness of Both Pieces

Before reaching for a screw, check the thickness of the material you're fastening.

For example, if you're attaching a relatively thin piece of timber to a thicker frame, you need a screw long enough to pass through the first piece and achieve good penetration into the frame — but not so long that it comes out the back.

This is particularly important with furniture, cabinets and other projects where an exposed screw point can ruin the job.

Don't Forget the Screw Head

The type of screw head also matters.

A countersunk screw is designed to sit flush with, or slightly below, the timber surface. Other screw types may sit on top of the material.

This can slightly change the effective penetration of the screw, so take the head style into account when measuring your job.

What About Pocket Hole Screws?

Pocket-hole joinery is a little different.

Because the screw enters the timber at an angle, selecting the correct screw length is particularly important. Too short and the joint may not have enough bite. Too long and the screw can break through the face of your project.

Your pocket-hole jig manufacturer's recommendations are a good starting point, particularly when working with thinner material.

And, of course, using a Robertson square-drive pocket-hole screw makes installation easy, with excellent engagement between the driver bit and screw.

Why We Prefer Robertson Square Drive

Once you've selected the correct length, you still need to drive the screw.

That's where the Robertson square-drive system really shines.

The square recess provides excellent engagement with the driver bit, helping to reduce slipping and making screws easier to control while driving.

For repetitive jobs — whether you're building furniture, working in the shed or tackling a larger woodworking project — that can make a noticeable difference.

There's a reason we say:

We Only Sell Robertson.

Not Sure Which Screw You Need?

If you're unsure about the best screw length, gauge or type for your project, we're happy to help.

Tell us what you're building and the thickness of the materials you're joining, and we can help point you towards a suitable Robertson screw for the job.

Explore our range of Robertson screws, driver bits and woodworking fasteners at Screw it Screws.