The bathroom renovation is under way. I’m at that exciting stage where I get to make the walls pretty with chair and trim moulding. Eeek!
The only problem is I had to contemplate ‘how in the world do I get these outside corners to work’!
Spoiler alert — it isn’t the same as cutting inside corners. If you don’t know what I’m talking about, let me explain.

Let’s dissect this wall because before you can do anything, you need to understand what part of the wall is the inside and outside. And when I say dissect, I’m just going to show because there isn’t much to it (I swear!)
The inside corners are where the walls meet, like the inside of a box.
The outside corners are the outer edges, like the outside of a box.
The end.

OK so now that we understand that, measuring the inside corner is pretty simple. You use a cheap protractor and divide that number 2. That’s what you set your miter saw angle to.
For example assuming that your wall isn’t square (because most aren’t), your inside corner is 88 degrees.
88 divided by 2 is 44.
Set your miter saw to 44 degrees and make your cut.
Now for the outside corner.
The process is similar but there’s one additional step. I’ll walk you through what I did on my wall.

I bought this protractor/angle finder for about $7 at Home Depot. There really is no need to buy an expensive digital angle finder unless that suits your fancy.

Hold the protractor around the wall making sure the edges are flush on the wall. Tighten the gold dial so the hands of the protractor don’t move — if it does, your measurement will not be accurate.

Let’s turn that around so we can read it. The angle of this outside wall is 85 degrees.

I must’ve lost my bearings along the way and I cut that 85 degree angle using the ‘inside corner’ formula (85 degree divided by 2) and this is what the moulding looked like. A mess. Repeat after me: this does not work on outside corners!!
So how did I correct this? I found the right formula after understanding why this didn’t work. I’ll tell you. This didn’t work because while miter saws and protractors both measure angles, protractors can measure up to 180 degrees. 85 degrees when cutting an outside corner does not translate the same to your miter saw.
So this is what you do:
180 degrees minus the angle divided by 2
In English, that translates to: 180-85= 95 / 2 = 47.5 <– this is your mitered angle.
I made the cuts again at 47.5 degrees and look at the difference.

Now they actually meet.

So much better, even if it is still waiting to be painted!
Be sure to follow the bathroom renovation on Instagram to see how it turns out.