How to Find the Right Swimsuit Size for Your Measurements | The Tape-Measure Method

One wrong size can turn a beach day into an adjustment nightmare. The fix is about three minutes with a measuring tape and a rule most shoppers skip: every brand sizes differently. A size 6 from one label might match an 8 from another, so relying on your dress size or a universal S/M/L label is the fastest route to a poor fit. Here is the exact measurement sequence that works for any swimsuit, plus how to apply it to real size charts.

What You Need Before You Measure

Grab a soft fabric measuring tape (the kind tailors use), a pen, paper, and a mirror. If you only have a piece of string and a metal ruler, that works too. Strip down to just your underwear or nothing at all — jeans and sweatshirts distort the numbers, and padded bras will inflate your bust measurement. Stand up straight in front of the mirror and do not suck in your stomach. You want the real numbers, not the aspirational ones.

The Four Measurements Every Swimsuit Shopper Needs

Bust

Wrap the tape horizontally around the fullest part of your chest. Keep it level across your back — check the mirror to be sure — and snug without squeezing. Record the number to the nearest inch. Nike’s official size guide uses this measurement as the primary fit input for its training swimsuits.

Waist

Find your natural waist, which is the narrowest part of your torso, usually just below your rib cage and above your belly button. Wrap the tape around that spot, keeping it parallel to the floor. Do not pull it tight enough to pinch.

Hips

Stand with your feet together and measure around the widest part of your hips. This is usually the fullest point of your seat and thighs. HAPARI’s guide notes that keeping the tape parallel to the floor here matters more than most people realize — a tilted tape adds inches.

Torso (Required for One-Pieces)

This is the step most people skip, and it is why many one-pieces ride up. Start the tape at the middle of one shoulder (where a swimsuit strap would sit), drape it down your back, through your legs, and back up to the same shoulder. The tape should rest gently against your body, not pull tight. Nike and HAPARI both list this measurement as essential for any full-piece suit.

How to Use a Brand’s Size Chart Correctly

Here is the rule that determines whether your swimsuit fits or fights you: the size chart you look at must come from the specific brand you are buying. Nike’s chart for its Women’s Training Swimsuit uses bust measurement only for its lettered sizes (XS through XXL). A different brand’s chart might use waist and hip measurements to determine the same letter. If you check the Nike chart below, then go buy a suit from a brand that sizes differently, the letter means nothing.

For a look at affordable swimsuit options from multiple brands that come in defined size ranges, check out our tested roundup of the best cheap swimsuits that actually fit well.

If your bust measures 35 inches, you would choose a size M from Nike. That same 35-inch bust might put you in a size S or L from another brand, which is why you must check the chart every single time. Baleaf also suggests reading customer reviews for “true to size” notes — shoppers will tell you if a brand runs small or large.

Five Common Swimsuit Sizing Mistakes

• Using a padded bra for the bust measurement. The foam adds inches that your suit will not fill. Always measure in your regular, unpadded bra or without one.
• Assuming S/M/L is the same everywhere. One brand’s small is another brand’s medium. Trust the inches, not the label.
• Pulling the tape too tight. A compressed tape gives you a smaller number, which leads to a suit that is too small and uncomfortable. Snug, not squeezing.
• Skipping the torso measurement for one-pieces. Without it, you risk a suit that rides up constantly.
• Sucking in your stomach. Your real waist measurement is what matters for fit, not the number you wish you saw.

When You Are Between Sizes

Swimsuit fabric stretches when it gets wet, so going with the smaller of two sizes is usually correct. The elastication in the suit will accommodate the difference. But there is a limit: if the swimsuit leaves red marks on your skin or is difficult to get into and out of, it is too small. Knix recommends ordering your usual size plus one size up and one size down when you are unsure — most online retailers offer easy returns, and trying the suit on at home is the most reliable test.

Prioritizing Comfort and Support

The right size on the tag means nothing if the suit is uncomfortable. Look for adjustable straps, a shoulder fit that does not dig in, and coverage that matches your activity (halter tops work well for bustier figures, bandeau styles for smaller frames). If you are buying a suit for swimming laps, the fit should be snug enough that the fabric does not catch water and create drag. If you are lounging, a slightly looser fit is fine. The goal is a suit that feels like it belongs on your body, not one you have to adjust every five minutes.