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Unlike jeans, there is usually no waist measurement included on the size tag of pants or slacks. This leaves some women wondering exactly what size to buy when it's time to update the wardrobe; or more accurately, where to begin.

If you are not using the sizing chart in a catalog, there can be a fluctuation of exact sizing. In addition, sizes vary from designer to designer. But there are some basic guidelines you can use to determine your approximate size range in the United States sizing system.

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Stand up facing a full-length mirror, and locate your natural waistline by finding the narrowest part of your torso. This is usually about the same level as your belly button. If there is no definition in your waist (no obvious dent), use the belly button location as a general guide.

Optionally, you can use a piece of string tied snugly and comfortably around your waist. Bend to each side and the string should move to your natural waistline.

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Stand up straight and exhale gently. Use a soft tape measure pulled tight against your body. Measure your waist, keeping the tape flat around your entire waistline. If you used the string method to locate your waist, measure over the string, even if the string is not completely straight. The number that intersects with the "0" on the tape measure is your waist measurement.

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Write this number down. For the purposes of these instructions, we will use the number 32, which according to Medical News Today, is the average waist size for American women ages 18 to 25.

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Stand with your feet together, wearing only your underwear. Measure your hips and buttocks in the fullest section. The number that intersects with the zero on the tape measure is your hip or "low hip" measurement.

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Write down your hip measurement.

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Find your waist to hip ratio by dividing the waist measurement by the hip measurement. Write this number down. This will come in handy just in case your ratio is over 0.8.

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Find your size by checking a catalog size chart. Find your waist measurement and look for the corresponding size. For example, a 32-inch waist, in most stores and catalogs will wear a size 12. Keep in mind that due to designer fluctuations, you could go as low as 8/10 and as high as 12/14.

If your waist is larger or smaller than 32, go up or down accordingly. For example, 31 inches would be a size 10 while 33 inches would be a size 14, etc.

If the number of your waist to hip ratio is greater than 0.8, consider going up a size from the chart in order to accommodate your fuller hip, despite your smaller waist.

Tip

Be sure not to take measurements while wearing shape wear, girdles, or other articles of clothing beyond underwear. They could influence your reading.

Unlike measuring for diet progress or some other reason, the best time to measure yourself for an accurate reading for pants sizing is when your pants would normally be the most uncomfortable, i.e. after a meal or after a glass of water.

Be sure to take an inseam measurement (from crotch to ankle) to get a general idea of your proper length. This way, you know whether to search for petite, average or long sizes when shopping for pants.

Be aware of vanity sizing. Though sizes have changed from the 1950s (Marilyn Monroe's 14 is today's 5/6), you could find yourself wearing a much smaller size than you intend when the label is pricier or in a major chain.

Warning

This is a general guideline and is intended as a place to start when determining your pants size.

You may not get a good measurement if you are bloated or experiencing abdominal discomfort of any kind.

About the Author

Toi Troutman

Toi Troutman, best known as a celebrity publicist and author of one book titled "Look Fab-Looking Like a Million Without Breaking the Bank," is now freelancing full time. The author of helpful articles published at various Internet destinations and beauty magazines including "Polished" and "LA Style," Troutman is a full-time journalism student where she is senior fashion beauty editor and news writer.