Blending sizes for a Pear Shape

I remember when I first started sewing and I didn't know where to start to make a garment that actually fit my measurements.  I was an XS chest and L hips at the time.  Part of what has kept me sewing for myself is that I figured that out and I actually have clothes that fit both my bust and my hips.
Since these are normal changes I always make to patterns I wanted to offer a bit of advice to anyone else trying to actually make clothing that fit.  I just finished my Wardrobe by Me Sille Blouse blogged here and figured it was a good time to share my method for blending sizes.
Before we start with size blending I want to take a moment to emphasize that changing width measurements for a pattern is important, but it is even more important to get the length measurements right first.  Scroll to the end for more about length measurements.
Where do you start?  First take your actual measurements.  Bust, Waist and Hips (the widest measurement you get in your hip area for me this includes the fullest part of my bum).  My Bust is 36", waist is 31" and hips are currently 45".
Now look at the body measurement chart for the pattern you want to sew.  Where do your measurements fall?

For this pattern my Bust is a 8, Waist is between 10 & 12, and Hips are a 16.  This is not quite enough information to pick what sizes I'll actually be blending though.  Now we have to look at the garment's measurements and the ease (amount of room built into the pattern for the fabric to hang nicely and give the designer's desired fit).

When I look at the Garment Measurements I see that there is a lot of ease in the waist and bust for this pattern.  I know I can trust the designer's chest measurement and will stick with the size 8 for my bust.  My waist measurement clearly isn't important here, because the ease is enough for it to easily fit even in the size 8.  Onto my hip measurement, okay my 45" hips do not fit in the size 8.  If I just make a straight 8 this will pool on my hips and puff out in my back.  Plus I won't have the desired ease the designer has built into the pattern.  Even if my hips did barely fit in the garment measurements of the size 8 I shouldn't make a straight size 8 if I want the blouse to look like the designer's line drawings.  After looking at where my hips fall on the body measurements chart and the finished garment measurements I decided to use size 14 for my hips.  Size 14 ends up having 4" of ease and will be close to the designer's desired fit without drowning my petite stature in fabric.  I didn't bother circling a size needed for my waist, because I'm just going to blend between size 8 and 14.  Ideally I want to be between size 10 and 12 around my waist.  What I want to focus on is having a smooth gentle curve between the sizes.  If you are new to trying this I recommend getting a French curve ruler to experiment drawing the new side seam.

For this pattern I stuck with the length of size 12, because I didn't need the extra lenght that is added to size 14.  I ended up removing 3" for my petite height anyway.
You can see I follow size 8 until just under my bust and then start curving out to size 14.  I know I need to be at size 14 before I get to my hips, so I make sure I reach the size 14 line a couple inches above the bottom hem.
What do I do for the back piece?  For a long time I would try and carefully copy the same curve (with measurements off of my French curve ruler).  Then one day I realized I could place the new front piece on top of the back piece and just copy it onto the back.  (Man did I feel dumb for all of my extra effort before)

Note I make sure the underarm seam is on the size 8 and the bottom is on size 14.  This guarantees that the side seams will be the same length.
I imagine there are some patterns that you cannot do this for.  Where the designer has intentionally changed the back and front side seam shapes where they don't match.  If you lay your front piece on the back piece and see that that is true you will instead have to make sure you follow a similar path (along the sizes) on the back seam.  That said I haven't had that problem since I discovered this trick.
Hope this helps someone.

For anyone who is more curious about why it is so important to get length (height) measurements right first.  What does that mean?  It means that if I blend out for a size 14 hips, but don't make the petite adjustment for my height then the garment will not fit right.  Basically if my hips are 3" higher than the garment is drafted for the blouse will puddle above my hips trying to get the widest part of the garment to the widest part of my body.  I'm 5'2" so 6" shorter than the 5'8" this pattern is drafted for.  Typically half of the height difference is in your torso and half in your legs, so I have a 3" difference I need to account for in this pattern.  When I remove the extra 3" I get the waist measurement to hit at my body's actual waist and the hip measurement to hit at my actual hips.  The same (but opposite length problem) would be true if you were taller than the pattern is drafted for.

Happy Sewing!