How to Choose the Right Size in Underwear and Bras

Quick answer

To choose the right size in underwear and bras, take accurate body measurements with a soft tape measure, compare them to each brand's size chart, and prioritize comfort and fit over the number on the label. Always check the specific brand's sizing guidance, as sizes vary between manufacturers.

Finding the right size in underwear and bras can feel like a guessing game, but it doesn't have to be. Whether you're shopping for yourself or someone else, knowing your measurements and how they translate to a brand's size chart is the first step to a comfortable, confident fit.

In this guide, we'll walk you through measuring for both bottoms and tops, explain how to use size charts effectively, and highlight common pitfalls—like relying on a previous brand's size or ignoring fabric stretch. By the end, you'll have the tools to choose pieces that feel like they were made for you.

Measure Yourself Correctly

Before you even look at size charts, you need accurate measurements. For underwear, the key measurements are your waist and hips. Use a soft, flexible tape measure and keep it snug but not tight. For your waist, measure around the narrowest part, usually just above your belly button. For your hips, measure around the fullest part of your bottom, keeping your feet together.

For bras, you'll need two measurements: your band and your bust. To measure your band, wrap the tape around your ribcage, just under your bust, and make sure it's level. For your bust, measure around the fullest part of your chest, keeping the tape parallel to the floor. Write these numbers down and use them as your baseline.

• Wear minimal clothing or underwear when measuring to get the most accurate numbers.
• Have someone help you measure for bra sizing to ensure the tape is level in the back.

Understand Size Charts and Brand Differences

Once you have your measurements, compare them to the size chart for the specific brand you're buying. Size charts can vary significantly between brands, so never assume your size in one brand will be the same in another. For example, a small in one brand might correspond to a size 4 in another, and hip measurements for a medium can range from 38 to 40 inches depending on the label.

Pay attention to the garment's rise and coverage. A high-rise brief will require a different fit than a low-rise thong, even if the size is the same. Brands often provide additional fit notes, such as 'runs small' or 'stretchy fabric,' which can help you decide whether to size up or down. If you're between sizes, consider the fabric's stretch and your personal preference for snugness.

• Always check the brand's specific size chart, not a generic one.
• Look for fit notes in product descriptions that mention whether a style runs true to size.

Consider Fabric and Style: Why Stretch Matters

The fabric of your underwear or bra plays a huge role in how it fits. Materials like TENCEL™, which is derived from trees, are known for their breathability and softness, but they also have a certain amount of stretch. A style with a single-layer design and low-pressure seams, like a dipped thong, will feel more minimal and may require a different fit than a brief with a wide-cuffed waistband.

For example, a brief with a supportive front panel and a higher rise is designed to minimize pressure on the lower abdomen, so you might want a snugger fit to get that support. On the other hand, a thong with a wider hip is meant to prevent digging in, so you might prefer a size that sits comfortably without being too tight. Always read the product details to understand the intended fit.

• If a product is described as 'barely-there' or 'airy,' consider how that translates to coverage and support for your body.
• For bras, adjustability features like straps and hook-and-eye closures can help fine-tune the fit.

Try On and Evaluate the Fit

Once your order arrives, try on each piece and evaluate the fit. For underwear, the waistband should sit comfortably without digging into your skin, and the leg openings should not ride up or leave marks. The gusset (the cotton-lined part) should stay in place without slipping. For bras, the band should be snug but allow you to breathe, and the straps should not dig into your shoulders.

Move around to test the fit: bend, stretch, and sit down. If the garment shifts or feels uncomfortable, it might not be the right size or style for your body. Remember that some fabrics stretch with wear, so a slightly snug fit initially may relax over time. However, if anything feels too tight or too loose, don't hesitate to exchange for a different size.

• Use the 'two-finger' rule: you should be able to slide two fingers under the waistband or bra band without it being too loose.
• Check that the center of your bra (the gore) lies flat against your chest.

Step-by-Step to Your Perfect Fit

1. Take your measurements: Use a soft tape measure to record your waist, hips, underbust, and bust. Keep the tape snug but not tight, and measure twice for accuracy. Checkpoint: Write down your numbers and date them—bodies change, so remeasure every six months.
2. Compare to the brand's size chart: Find the size chart for the specific product you're eyeing. Match your measurements to the chart, noting any fit notes like 'runs small' or 'stretchy fabric.' Checkpoint: If you fall between sizes, size up for a relaxed fit or down for a snugger feel.
3. Consider style and fabric: Think about the rise, coverage, and material. A high-rise brief fits differently than a low-rise thong, and stretchy TENCEL™ may conform more to your body. Checkpoint: Read product descriptions for details on seams, waistbands, and support features.
4. Try on and assess comfort: When your order arrives, try on each piece. Move, bend, and sit to test for digging, riding up, or slipping. Ensure the bra's gore lies flat and straps don't dig. Checkpoint: Use the two-finger rule for waistbands and bra bands. If anything feels off, exchange for a different size.
5. Adjust for your body: Remember that sizes vary by brand and even by style within the same brand. Don't get attached to a number—focus on how the garment feels and functions for your unique shape. Checkpoint: Keep a note of your favorite brands and sizes to streamline future shopping.

Products that Help You Find Your Fit

• Low Profile Thong 3-Pack: A three-pack of our fan-fave Low Profile Thong. A super-sleek, low-mid rise staple without any unnecessary bells and whistles. Lined throughout for a body-hugging feel and secured with a flexible zig zag stitch, this smooth & supportive thong is an everyday essential. Made with super-soft, tree-derived TENCEL™ fibers known for their breathability. Our signature gusset is full coverage (no lip slips!) and knitted... If you're new to thongs or want a consistent fit, this three-pack lets you test the same style in multiple sizes without committing to a single pair. The lined, body-hugging design and full-coverage gusset help you evaluate what a secure, comfortable thong feels like.
• Brief 2-Pack: A two-pack of our classic Brief. Delivering next-level comfort with our highest rise, wide-cuffed waistband, and supportive front panel, this cut feels like a hug and minimizes pressure on the lower abdomen. The modest-cut leg is elastic-free to keep you moving freely—with just a peak of cheek. Made with super-soft, tree-derived TENCEL™ fibers known for their breathability. Our signature full-coverage gusset is... For those who prefer more coverage, this brief offers a different fit reference. Its wide-cuffed waistband and supportive front panel highlight how a higher rise can affect sizing—you may need to size up or down compared to a thong. A two-pack gives you a backup while you dial in your perfect size.

Choosing the right size in underwear and bras is a mix of accurate measurements, understanding brand-specific sizing, and paying attention to fabric and style. By following these steps, you'll avoid the frustration of ill-fitting pieces and enjoy comfort that lasts all day. Remember, the best fit is one that makes you feel confident and at ease—so don't be afraid to try different sizes until you find your match.