A circle is 360 degrees, so if you should end up with 16 petals, that means each one (excluding seam allowance) is 22.5 degrees.
Check your angle ruler, if it is 17 degrees, then you'd need 21 petals (and skimp a bit on the seam).
It does not take much of a difference in the wedges to make a large difference in number of petals needed.
The part I have trouble with is I tend to start my seam a bit wide and then narrow down, this will change the angle slightly, and can mean you now have a 24 degree angle instead of a 22.5 degree angle, You will know this is happening if you find your ending circle is either larger or smaller than you expected.
Last edited by Macybaby; 06-20-2018 at 07:07 AM.