Get comfortable with the person who is going to help you take measurements. For most accurate results, wear only your bra and underwear.
Wrap the measuring tape around your bra from the back, setting it across the fullest part of your bust, or the largest area of your breast. Write down this measurement in inches or centimeters.
Move the tape measure down under your bust. If you are a large-busted gal, you may need to lift the girls a little to get this measurement. Stick with the same units -- inches or centimeters.
Measure your waist. Your waist may seem like it spans more than one place, but the best location to measure for a corset is at the narrowest part of your waist, just under the bottom of your rib cage.
Find the top of your hip bones, which are about the same level as your belly button. Remember that each woman is created differently, so don’t worry if you have trouble finding your hips at first, or if they aren't in the exact same place as another woman’s.
Measure around the top of your hip bones, and record this measurement. If you are purchasing a longer corset, one that will extend down beyond your waist, measure the fullest part of your hips, where your hip bones are the widest.
Go to a corset manufacturer or visit the manufacturer’s website. Each corset maker has a different sizing chart. Some will instruct you to simply supply your measurements to determine your size, while others will tell you to order a specific size if your results are above or below specific measurements.