You might add that to cut PVC accurately you will need a PVC cutting tool or a table saw or some sort of miter saw.
The last too are over the top unless you have one handy.
PVC Cutting Tool, this thing is a snap to use I have had one for years.
Hack saws will work your tail off and they leave fuzz in the pipe you have to get rid of.
They are hard to master and you need a good one.
You want your cuts to be as square and as accurate as possible.
18 inches should not be 18-1/8.
So you will need a good tape measure.
I have several and the two I like the best are the Stanley 12' metal cased ones like this.
Then from my experience I like to mark PVC with a fine point sharpie.
Once you have cut off a length of pipe to the right length write P on it.
Use this piece to mark the rest that length.
No reason to keep measuring pipe over and over again when you dont have to.
DO NOT use the last piece you cut to mark the next piece.
Use the first one always.
If you dont the pipe will get longer and longer.
My mother learned this the hard way with a patchwork quilt.
Find a place to work at waist level or higher.
I like to put my pickup tail gate down and sit in a chair to do monotonous work.
Trying to do all of this cutting and assembly on the ground will kill your back.
Next if you have ever tried to take PVC out of a fitting after it has been put together all of the way it can be real hard sometimes.
I would suggest you get emery cloth and sand down all male ends a wee bit.
Here is what it looks like.
We do want our tomato cage to look good and not be a pain to build.
Making things should be fun.
Good day.
Worth