woodworking measuring tips

5 Woodworking Measuring Tips To Avoid Costly Mistakes

Measuring is a critical skill to learn to avoid making costly mistakes. Learn these woodworking measuring tips to have better success with your projects.

I’m sure you’ve had this happen: cutting a piece of expensive hardwood and then realizing it is the wrong size! 

If you are lucky it will be too long or too wide, which just requires another trip to the saw to trim it to size.

However what usually happens is that the piece is too short! And you can’t hit the “Undo” button on your saw to fix it. You can either splice two pieces together or use the too short piece for another part of your project and hope you have a longer piece you can use.

Let’s have a look at some woodworking measuring tips, so that you can avoid these measuring mistakes.

Nominal dimensions don’t equal the actual dimensions

Lumber in North America is usually sold in the nominal, not actual dimensions. Nominal basically is for rough, unplaned lumber as it is sold and priced.

So you will see 2×4’s, 1×8’s and 2×2’s. But in reality the actual dimensions are quite a bit smaller. This page gives a good overview of the relationship of actual vs. nominal sizes.

So if you base your project on the nominal dimensions, you will run into problems. Even plywood that is sold as being a certain thickness often is 1/32″ undersized. A 1/2″ piece of plywood is usually 15/32″ thick.

It’s often better to design a project that requires precise joinery once you have the wood you will be building it from. Then you can measure the actual dimensions of the lumber to make sure any plans you create are accurate. 

Use a tape measure properly

Tape measures are incredible tools. A lot of thought and refinement has gone into making a tape measure an indispensable tool.

Here are some common mistakes made though when using a tape measure:

Not using the end hook properly – The end hook of a tape measure is attached loosely for a reason. When you measure an outside measurement you need to pull the tape tight so that the hook extends fully. When you measure an inside measurement, you need to push the tape tight so that the hook retracts fully and makes up for the thickness of the hook. Any dirt or foreign material in the hook’s hole could affect this action, so remember to keep your tape clean.

Trying to use it for precise, small measurements – A tape measure is not designed to measure 1/8” or have the precision to dial in a fence for cutting precise joinery. You should instead use a steel ruler or for measurements under a few inches, use a dial or digital caliper such as this one:

Use the right marking tool

A carpenter’s pencil is a useful tool. It was though designed to mark rough wood to cut it to rough dimensions for planing and other finishing work prior to cutting it to the final length.

I use it when marking lumber for my outdoor projects. If a measurement is off by 1/16 of an inch it’s not such a big deal. It’s for the most part rough carpentry anyways.

If you do use a carpenter’s pencil, make sure you sharpen it correctly. You can use the old method of whittling with a utility knife. But the best way is to buy the following:

The best method though of marking lines is still a marking knife. The thinner the line, the better. Plus the slight groove a marking knife leaves can be used to position a chisel. 

Keep in mind though that if you make a mistake, knife marks are hard to remove. It’s best not to make too deep of a grove so that marking mistakes can be sanded or planed out.

Finally you can also use a mechanical pencil if you really want pencil marks instead of knife marks. The good thing with a mechanical pencil is that the lines will always be the same width and no need to have a sharpener handy (just enough pencil leads).

Be clear on what part is waste wood

Has this happened to you?

You mark a line with precision. Then cut on the wrong side of the line! Now your piece is short by a saw blade kerf.

To avoid this, make a small mark on the waste side of the cut. I usually make an x. Like this:

Cut line waste mark

Make your mark small and close to the cut line so that the actual cut will remove the mark.

If you are cutting out a section to be discarded (such as notching a corner of a piece of plywood to fit around a frame), put a big X on the waste piece. This also applies to joinery where you want to mark the parts of the pieces that are being cut away.

Using measurements exclusively

I’ve seen many woodworkers just go ahead and follow published plans and cut all the wood for a project at one time. Usually these are experienced woodworkers that are confident in their measuring abilities but even they make mistakes at times.

This is an efficient way to work, however sometimes mistakes creep in, especially on more complicated projects. Sheet goods such as plywood are notoriously bad for being undersized. 

I prefer to cut pieces as I need them. This way I can measure pieces against the project. It’s slower but I save time and wood in not having to recut or discard pieces that end up not fitting.

There are two ways to go about this:

  1. Measure with a measuring tape, ruler or calipers: sometimes though small errors occur due to variances with measuring for the part and then measuring again for the cut line.
  2. Measure directly against the project:. If you need a piece to span between two other pieces, hold the piece in the correct position and then mark the cut line with a marking knife or mechanical pencil. This also goes for joinery. Use the piece that will mate with the other piece to mark width and depths of dados, rabbets and half-lap joints for instance.

Mistakes do happen. It’s just the nature of projects, especially the more complicated ones. But as you gain more experience, mistakes become less common, especially if you follow the woodworking measuring tips above.

Also keep in mind that if you are adapting an existing plan or design that you need to be really careful that mistakes don’t creep in.

Good luck with all your projects and here’s to measuring twice and cutting once!

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