Today I will answer for you a question that I often see asked in online corset communities. I've touched upon this in one of my posts for The Lingerie Addict, 3 Most Common Corset Lacing Mistakes, but here I'll be going into greater depth. Just where is your waistline, and where should you wear your corset?
For a modern audience, many of us think of our waistline as where the waistband of our jeans rests. From a dressmaking standpoint, this is actually called the "high hip," and not part of the waistline. The "natural waist," or, "apparent waist," is the visually narrowest part of the torso, generally about an inch above the belly button. High-waisted skirts and pants or dresses with a waist seam utilize the natural waist and it's an important point of reference for fit. As there is such a variance in body shapes in proportion, of course, your natural waist may be in a different position or less obvious.
Neither of these, however, is the waist level where you'll settle your corset. For comfort and maximum reduction, it's best to cinch your corset to your skeletal waist. The skeletal waist is the space between the bottom of the rib cage and the top of the hips. Many people assume that their ribs end at their apparent waist, and when they realize this isn't so, they then assume that their body is "weird." Nope, your body's not weird! First of all, there's a lot of natural variance, but it's actually pretty standard for the lowest ribs to be below the apparent natural waist. So when you lace on, make sure your corset is settled at the skeletal waist to avoid putting undue pressure on your ribs. Proper waist placement will also provide better support for the stomach and low back, and help the hips of the corset to fit smoothly.
Corset neophytes often try to lace their corsets to their apparent waist, then get concerned when it naturally settles at the more compressible skeletal waist. Better to lace to this level from the get-go and enjoy the extra cinching (and comfort!) it will provide. If you think your corset might be settled too high on your waist and you've already laced up, there's an easy fix. Firmly grasp the bottom of the front of the corset with both hands. Holding it in place, inhale upward, arching your back. This will stretch your spine and raise your ribs above the waist of your corset.
Personally, I tend to wear my corsets a full inch below my apparent waistline. You can really see it with the long ribs and sharp hip spring of the Gibson Girl. Speaking both generally and specifically, the sharpness of the hip spring is tied into the length of the waist - or rather, the level of it, with a lower waist corresponding to a sharper hip spring.
The space between the top of your pelvis and the bottom of your rib cage can also vary quite a bit. Short-waisted individuals may have as little as half an inch between these bony masses, whereas someone long-waisted may have three or more inches of compressible space.
Lastly, be sure to take this variance in waist placement into account when taking your vertical measurements! It's for this reason that I prefer to use separate waist to underbust and waist to lap measurements, rather than a continuous torso/princess/busk length as reference. It's entirely possible for two individuals to have the same underbust to lap measurements, but different waist levels within that range. So the same corset might leave one wearer's stomach unsupported while prodding into their bust, while on another individual expose the ribs (creating a pinched roll between bra band and corset top) and instead poke into the lap, making sitting difficult.
The Corsetrix, Pop Antique