How to Cut a 135 Degree Angle on a Miter Saw

A miter saw can cut across the wood at various angles. That is why it is the preferred saw when it comes to cutting boards for joints. But when it comes to cutting obtuse angles for joints, there is a little math trick you can use. So we came up with a guide to help you understand how you can cut a 135-degree angle on a miter saw.

Woodworking is not just about the tools, you also require skills and mathematical knowledge. People often usually do things with their eyes and do not pay attention to the maths. But then they fall short of measurements and they have to do things all over again. Woodwork requires precise calculations with some margin for error. Like cutting a 135-degree angle on a miter saw, it requires knowledge of geometry and angles in particular.

Why Use a Miter Saw to Perform Angle Cuts?

A miter saw is pretty much a circular saw but it sits atop a frame that can lock itself in a place. So when you perform the cut by moving the blade down, it cuts across straight. The stability you get from the miter saw is unparalleled. And thus there is very little error when it comes to using it.

The whole thing is based on measurements that are mentioned all around the saw. The angles are mentioned under the saw near the fence. The tilt angle is mentioned behind the saw and can be measured from there. The length is mentioned near the fence where you can measure that.

So when you are using the miter saw to perform an angle cut, you lock the blade in the angle. And when you lower the blade to perform the cut it makes a clean cut in the mentioned angle without any error. Of course, you also have to account for the KERF, which is the width of the blade. When you factor in all of these then you get unparalleled mathematically accurate cuts.

How to Cut a 135-Degree Angle on a Miter Saw

When you look at the miter saw, there is no mention of a 135-degree angle on the scale. In fact, a normal miter saw might have up to 45-degree of angle on each side of the scale. So cutting obtuse angles might seem like a difficult job for most people. But if you know your math right, you can cut a 135-degree angle on a miter saw with ease.

So basically when you mean cutting a 135-degree angle on a miter saw, you mean two pieces of wood joining to create that angle. After cutting two pieces of wood in the formation of a joint, you can join them and they will have that angle.

So using an acute angle that is on the miter saw you can actually achieve a joint with an obtuse angle. Just to clear things for people who do not know what obtuse means, it is an angle greater than 90-degrees. The acute angle is an angle less than 90-degrees. And a perfect 90-degrees is called a right angle.

Formula to Cut 135-Degrees on a Miter Saw

There are two formulas that we can use to cut at an obtuse angle. Both of them yield the same results, so using either of them works. Using the answer to that formula you make inside cuts and then join the two pieces of woods to provide the desired angle. In this case, it is going to be 135-degrees.

  1. 180-Angle=X
    X/2=Angle for Miter Saw
  2. Angle/2=X
    90-X=Angle for Miter Saw

Let us use this formula to find the angle we need to cut to achieve the 135-degrees. We can use either of the formulas, we will use both to prove that.

  1. 180-135=45
  2. 135/2=67.5

This proves both formula work, and the angle requires on the miter saw to achieve a 135-degrees cut is 22.5-degrees.

Now let us walk through the process of how you will do this.

Step 1)

First, unlock the knob for the angle cut and move it to the left on 22.5-degrees. You then lock the miter saw in that angle. You also need to make sure that the tilt angle is on 0-degrees. Meaning it will cut straight across and not in a bevel formation.

Step 2)

If you are using a longboard, make sure to clamp it to the miter saw. If you are using a smaller piece of wood, then hold it firmly against the fence so it does not move while performing the cuts.

Step 3)

Cut the first piece of the wood inside at the 22.5-degrees. After that, you move the miter saw to 22.5-degrees on your right.

Step 4)

Take another piece of wood and make an inside cut across it at the 22.5-degrees on the right. Once you have cut both of these pieces together at the cuts and they should align perfectly.

Step 5)

Take an angle measuring tool and measure to ascertain you have reached the requirement of 135-degrees or not. A .1 degree of difference is negligible at most so do not worry about that.

With this, you have now cut 135-degrees with a miter saw. You can use the same formula for other obtuse angles as well.

Things to Be Careful About When Using a Miter Saw to Make Angle Cuts


  • When you are trying to cut using any power tool, always take safety measures. Wear safety equipment when you operate a miter saw, so you are protected against severe injuries during an angle cut. When cutting wood always wear goggles so your eyes are protected from saw dust. Always wear a mask as well so you do not inhale any sawdust as well. Wear earmuffs to protect your ears from the loud noise of a miter saw.
  • When making an angle cut, always lock the knob at the angle you want to cut at. Locking the saw at the certain angle will ensure you make a perfectly straight cut. This provides your cut with more stability. These locks are there for this reason on the angle cut and the bevel cut.
  • If you are cutting a big piece of wood on the miter saw, make sure to press it against the fence tightly. This will allow the miter saw blade to make a clean and straight cut across. If the wood is not pressed tightly against the fence, it might wobble while being cut and ruin the straight cut across.

Makita 10″ Compound Miter Saw


Speed: 4600 RPM
Dimensions: 20 x 10 x 21 Inches
Power Source: Corded Electric
Miter Cuts: 0°- 45° to the left and 0°- 52° to the right
Positive miter stops: 15°, 22.5°, 30°, 45°, right or left and 0° (90° cuts)
Included Components: 10″ 40T Micro-Polished Miter Saw Blade, Dust Bag, Triangular Rule, Vertical Vise, Socket Wrench

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As important as woodwork equipment is, knowing how to use them can make your life so much easier. This is specifically important for DIY enthusiasts. With a plethora of woodwork tools in the market, knowing how to use the one that meets your requirements can smooth sail your DIY projects. By using this formula, you can find out any obtuse angle cut using a miter saw.

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