How to Measure and Mark Lumber

Back in high school, I took two courses that changed my life. The first was an art class, which launched me into a career in the arts. The second is the drawing class. Little did I know that drafting classes would be just as important. In many drawing classes since, I think this taught me how to measure and mark lumber more than anything I ever learned in my wood tech class.

Marking with a knife, pencil or crayon?

For ultra-high precision when measuring and marking wood, do not use a pencil. Use a utility knife instead to mark the wood. A sharp pocket knife with a small blade or a specially marked knife designed for this purpose will also work. For everyday marking on wood, I use a 0.7mm mechanical pencil. The lead on a 0.5mm mechanical pencil is a bit too flimsy. It breaks too much and the 0.9mm lead is a bit too thick. For rough, unfinished wood, I keep a 0.9mm pencil handy. For very rough wood, including bark, use a wood crayon. Sharpie markers also work well on wood. Just be aware that they will soak into the wood and ruin any finish you use later.

Measure and Mark Plywood

Let's start with a sheet of plywood. From that sheet, I want to cut out a piece that is exactly 24 x 48 inches in size. This assumes the factory edge is correct. In the image below I demonstrate how to make a plywood with three crow's feet. A crow's foot is a triangular mark where two points meet at a precise point. This location is the point you want to measure, in this case 24".

I drew three crow's feet to satisfy the age-old axiom "measure twice, cut once". If I only made two marks and one of the measurements was wrong, I'd ruined the plywood when I was cutting it. If I make three markers and miss one of them; I'll know right away because someone's going over the line. When I draw the line or place my Festool TSC 55 KEB track saw over the mark, all three of them should line up perfectly. Part of measuring and marking accurately is preparing yourself so you don't make costly mistakes.

Place an X on the scrap edge of the cut

When I draw my connecting lines, I want to put an X on the waste end of the line. This is the side I plan to "give up". If I didn't mark it, I might get distracted and accidentally cut the wrong side. This wastes both material and money. There is an X on the scrap side of the thread and I know to always put my saw cuts on that side.

Measure and mark plywood to reduce waste

Now suppose you have a new piece of plywood and need to cut three 32 x 40 inch panels. For this exercise, we will ignore the kerf. The direction I lay out the lines determines whether I can fit all three sections on one sheet. In the first example below, I can only get two panels out of one sheet. In the second I installed all three panels. Always plan your cut before you pick up the saw!

Just like planning your plywood cuts, it pays to plan your gauge lumber cuts. In the first example below, I am able to get all the wood in the cut list. In the second example, I am not.

One trick is to always start with the longest section and work your way up to the smallest sections. Do this instead of starting at the top of the list and going to the bottom.

Hey, where is the last 8ft plank in the example above? Starting from the top of the cutting list means someone has to go back to the home center to pick up another material!

Find the center of a rectangular object

Continuing with our mental measurement and labeling exercise, let's imagine we cut plywood into rectangles of various sizes. We need to find the exact center of each. The easiest way to do this is to draw a diagonal line connecting the corners. Regardless of the shape of the rectangle, the center is always where the two lines meet.

In other words, the X marks the location!

Let's say we found a piece of plywood and we wanted to make sure it was square before using it. We can go all the way back to our truck and get a frame square, or we can measure the diagonal drawn above. The only way the two diagonal measurements will be the same is if all four corners of the plywood are at perfect 90 degree angles.

Measure and mark with 3-4-5 triangle

Maybe you found a piece of plywood that you need to check to see if it's square, but all you have is a box of 12" kids' rulers. Can you check that the corners are still square? With a 3-4-5 triangle, you can. In the simplest terms, any triangle whose sides have a ratio of 3-4-5. In other words, 3 inches on one side, 4 inches on the other, and 5 inches on the last leg (could also be feet or meters, not just inches). Since they are proportional, we can multiply one number by all three sides to make the triangle larger for greater accuracy. For example, if we use 3. We get 9 inches on one side, 12 inches on the other side, and 15 inches on the last leg. This is something our rulers can handle.

Find the center of a strange shape

Sometimes you have a situation where a tape measure, ruler, laser, or other measuring device won't work because the object you're measuring is curved or irregular. To get around this, I rely on wires such as mason wire or tar bank wire. To calculate the length of an irregular or curved object, run the rope around the outline. Then measure the length of the rope to find the total distance.

If you don't have a tape measure with you, you still need to find the center. Fold the rope in half first, then put the rope back around the outline. When you run out, you will be in the center. If you fold the rope in half again, you'll find the 1/4 mark.

This trick of folding the string in half also works with a tape measure when you need to do some quick math. If you measure something with a tape measure and need to find the center, fold the tape measure in half and look at the center of the crease to see what half the distance is. I've found this to be accurate enough most of the time, unless I need to be exactly centered.

use story stick

In college I trained as a minor in joinery. My teacher used something called a story pole which is a long 1" x 2" piece of wood. Length may vary by project. Here you mark all key measurements of the cabinet. The idea is that if all your cabinet doors are supposed to be 24-1/2 inches wide, you can measure it every time, but chances are you might be off on some of them. Instead, you take the story pole and mark 24-1/2 inches on it and write "Cabinet Door". Use it now to measure all your cabinet doors. Even if it's slightly off, at least all the doors will be off by the exact same amount, so it won't be noticeable.

Story Rod has all your key measurements. Mark everything that needs to be repeated – styles, rails, toe kicks, etc. When you're done with a project, the story pole tells the "story" of the project with all the measurements and marks you've made on it.

If you're doing this for a client, they might even appreciate being able to keep the pole after you're done.

centering ruler

There are many specialized measuring and marking tools that can make life easier, but as you will see later, they are not necessary. The first is to find the center of the ruler. This is a ruler that starts at zero (0″) in the middle and averages out from there. If you need to find the center, align the same measurement on the left and right sides of the ruler. Once you do this, the zero mark will in the exact center.

Marking gauge

The second tool is a marking gauge, which is a traditional carpentry tool. It consists of a long beam called a rod, usually about 8 or 9 inches long. Surrounding it is a movable guide fence that you can move against the wood. Protruding from the end of the stem is a spur, a short spike used to score wood. I could write an entire article about marking gauges and you can find a great video made by Stumpy Nubs.

Sliding Tee Bevel or Bevel Gauge

A sliding tee bevel, also known as a bevel gauge, is a device used to measure and communicate the angle of wood. It's often paired with the simple protractor you used in elementary school. It consists of a removable thumbnut or thumbscrew, a beam, and a buttstock. The stock is placed against the wood and the beam is moved to the angle you need. Then tighten the thumbscrew to lock the angle in place, and you can transfer it to another piece or piece of wood for measuring, scoring, and more.

Measuring and marking lumber is a skill that you will get better with time as you find your own technique. Watch out for the old guys on the construction site. They know a variety of techniques for different situations, and most are happy to pass on their knowledge.

If you have some tips of your own, feel free to leave them in the comments below. thanks for reading!