This article is a transcript of the video “How to Determine Your Internal Waist Measurement” on Youtube. You are free to watch that video (which shows a demonstration of the process):

Have you ever had a situation where you purchased an OTR corset of a specific size, say 24″ waist – but when you closed the corset completely in the back, you realized that your waist measures more like 25-26″ on the outside? Why do you suppose this is? Shouldn’t a size 24″ corset give you a final external circumference of 24 inches around the waist?

There are several reasons why the corset may be larger than its stated size: the corset materials may have stretched slightly over time (all fibers have a certain amount of stretch), the corset may have been mislabeled, but more than likely the corset itself is true to size on the inside, and it’s the bulk of the bones and fabric itself which is causing the larger external measurement.

How are Corset Sizes Determined?

The waist of a corset starts with the pattern drafted. A pattern is a 2 dimensional representation of the corset panels on paper, which you cut out and use to trace the fabric. If you were to measure the width of each pattern piece at the waistline of the corset pattern of this Morgana Femme Couture corset, you’ll see it has a total circumference of 22″ (11 inches on each side).
This means that the corset when laid out flat (and not taut around the body) determines the size at the waist.

If you purchase a new corset, lay it out flat and measure it at the level of the waist tape – it should reflect the size of the corset. If you have a well-used corset that measures larger than the tag size even when laid flat; this means the corset has stretched over time.

So why would a corset on the body be bigger than 22 inches on the outside?

The corset itself takes up bulk and volume. All matter will take up space. Even in a corset with both the fashion side and the lining side being 22 inches, the outside of the corset will have to stretch a little to account for the bulk on the inside. Some corsetieres will roll-pin, use turn-of-cloth, to make the outside of the corset a little larger so that it doesn’t stretch or cause wrinkles. I have a separate video explaining the science behind that.

How to find your internal waist measurement while corseted

Side note: doing this often can stretch out your tape measure over time. Do occasionally compare your tape measure units against a yardstick or carpenter’s tape, to ensure that it hasn’t stretched. (Photo from Pixabay)

To determine how to find the internal waist measurement or the true restriction on your waist, first wrap a flexible tape measure around your waist at the smallest point. (It helps to wear a slippery shirt for this as you will be adjusting it as we go along.) Hold the tape in place as you wrap the corset around your body and slip the measuring tape through the slit between the busk, then start tying up your corset.

*Please note that this method only works if you have a busk or front lacing in the front of your corset. If your corset has a closed front, a zipper, a stiffened modesty placket under the busk etc, then you will have to position the ends of the tape toward the back and have a friend read it for you (or take a picture).

As you’re tightening your corset, stop periodically to make sure that the tape measure is still positioned in the proper place at the smallest part of your waist, and that it’s not twisting or bunching up under the corset. Keep tightening little by little and pull the tape measure so it remains smooth. (This is where the slippery shirt or liner comes in handy.)

Once you have your corset closed  (or tightened to comfort), adjust the measuring tape so you can read it – don’t pull too hard otherwise you may change the reading, but move the tape to the side so the difference can be taken. You’ll see in the video that my 22″ corset has an internal reading of 22.25 inches, with a tiny gap at the back. When I measure the outside of my corset, it reads 23.5 inches which means the bulk of the corset itself adds about 1.25 inches to the circumference of my waist.

A way to calculate the bulk of a corset

There is a way to estimate the external vs internal circumferences of one’s waist  (thanks to Lexa, to Albert of Staylace, and to 1sdburns for pointing this out) – if you imagine that a corset is 5mm thick on average, this means that when the corset is wrapped around you, it adds about 5mm to the radius of your waist (from the center out to the edge), or 10mm to the diameter (from the outside of the corset on one side of your waist, to the outside of the corset on the other side). If you use the equation for relating radius to circumference:

5mm* 2(pi) = 31.4mm (which converts to about 1.24 inches)!

This method of calculating the thickness of a corset will be more accurate if you have a corset with sandwiched boning channels and a very regular thickness all around – if you have a corset with lots of external boning channels with areas of “thinner” corset in other places, this method may not be perfect.

What if you need a specific external waist measurement?

Experienced corsetieres will have an idea of how thick their corsets typically are, and so if you have a situation where you need a specific external corseted measurement (say you need to fit into a vintage dress that is no larger than 24″ in the waist) then the corsetiere may be able to create a corset that gives you that external measurement, drafting the internal measurement slightly smaller.

If you plan on buying an OTR corset to fit into that dress, then I would advise buying one size smaller than you think you need – so purchase a corset with a 22″ waist to go under that 24″ dress – but be sure that the ribcage and hips of the corset will be large enough to accommodate your natural measurements in those areas so you don’t experience pinching or discomfort.