Step one: Make yourself a cup of tea.
Once you have your cup of tea you will be ready to start.
As promised here's your free pattern BUT WAIT DON'T JUST USE IT WITHOUT READING
This pattern was drafted for MY body, not anyone else's. Because I know my measurements, I can extrapolate what someone else's pattern should look like by getting their measurements and adjusting. Some notes about my body shape: I'm male, I'm fairly fit and muscular. I have really large pecs for a guy. Take these things into consideration when adjusting this pattern for your own use.
Here's a measurement diagram for you
With these measurements, you should be able to draft your own pattern based off mine. For example, I've just drafted a pattern for a vest for Roki, who is a much larger guy than me.
Start with your center front AND center back. Use those "Neck to chest, neck to waist, neck to hip" measurements and mark points along that line. It's easiest to line up the front and the back with the chest measurement, see how that red line on the pattern goes?
Then take the appropriate measurement and draw out at right angles from the center front line til you reach the correct point. For example, my chest measurement is sitting at 103cms at present. I measured out 30cm. If you multiply that by two you get the measurement across the entire front. I let the back measurement be a little smaller at 25cms. So that gives me a total of 110 - a good 7cm more than my actual chest measurement. This allows for movement. You may find that you want it looser than that, or you may not.
The same process applies to the waist, and then you join these two points. Depending on your body type you may do a straight line, or inward curve like I have, or outward curve, or inward only on the front, etc etc.
"But wait mr Pointy McMando, what's that I see? A dart? How do I deal with that?"
Yup, there's a dart in the front there. Remember I said I have massive pecs? If I didn't dart the front, I'd have issues with the sides being really loose and horrible under the armpit. This is why this pattern will work for ladies too - and you can experiment with making the dart wider or narrower as needed to fit your body type. You only measure the waist along the line that won't be taken away by the dart though - see how that red waist line breaks? It's the red that's the measurement only. Otherwise you're suddenly going to have to get a whole bunch skinnier
Once you have all of those side bits done, you can move on to the neck. Generally speaking you want the front to dip lower and the back to sit higher. Have a look at a T shirt you have, see that it does exactly that. That's the look we're going for here. So my neck measurement is 41cms, the back neck measurement on the pattern is 10cm and the front is 16, making the entire round trip be 52cms. So there's a good 4" ease there to allow me to breathe. Note: I did MY neck measurement choke collar style, not as is suggested in my measurement diagram. A T shirt will already have a little ease, hence the pattern says add 2" ease not 4".
Draw in a curve that looks right. Seriously, that's how scientific this is
And make sure the measurement matches. If the curve looks like the curve on a T shirt that fits you closely? You're winning.
Once the neck line is drawn, you can do the shoulder line. On the front this is pretty easy, it's just a straight line slightly shorter than your actual shoulder measurement. On the back, I find that if you give it a slight curve as you see there, you avoid some bunching up around the top of the armhole. Both the front and the back shoulder lines should be the same length.
The armhole is last. Please note again, I have large pecs - other people's vests that I've made have ended up with a less pronounced bite into the front, and slightly more pronounced bite into the back, than this pattern because of that.
Yes, add 6" ease. You want to be able to move your arms right? Again, draw the curve to how it looks right, from the end of the shoulder line to the point where your chest measurement came to before.
You have a pattern.
Now sew it IN SCRAP FABRIC/CALICO FIRST to make sure it fits, make sure you can move, see what adjustments you need to make, see how much you need to curse my name to the high heavens.
How you decide to join it is up to you. I tend to like doing a single size zip plus a zip on one shoulder seam. Remember if you go with velcro to add enough material for the overlap - this pattern only goes to the actual seam.
Here's me making Roki's pattern -
He's a much larger guy than me...
And here's Swift's vest which I made using the same method -
And now you're going, BUT SHOULDER BELLS HOW DOES I DO THEM WAAAH
Take your actual shoulder bell
Trace around it
Add about half an inch plus whatever you're comfortable with seam allowance being
Only now that you have read the entire post may you use my free pattern to its full potential!
Oh yeah, last step? Have another cup of tea.