How to Shop for Swimwear Online Without Getting the Size Wrong

Quick answer

To avoid the wrong swimwear size when shopping online, measure your bust, underbust, waist, and hips right before you order, then compare those numbers to the brand's size chart rather than your usual clothing size. Prioritize adjustable features like halter ties and stretch linings, and check the return policy before buying. If you're between sizes, size up for comfort and use the adjustment straps to fine-tune the fit.

Buying swimwear online can feel like a gamble, but it doesn't have to be. The key is to treat sizing as a measurement exercise, not a guessing game. Most size mistakes happen because shoppers rely on their dress size instead of their body measurements.

This guide walks you through a practical swimwear measurement routine, how to read size charts, and which fit features to look for in bikini tops and bottoms. You'll also find decision rules for common dilemmas like being between sizes or choosing between a push-up and a plunge style.

Measure yourself correctly before you order

Use a soft measuring tape and wear a non-padded bra or no bra at all. Measure your bust at the fullest point, your underbust snugly against your ribcage, your natural waist at the narrowest point, and your hips at the fullest point. Write these numbers down in inches or centimeters—whichever the brand's size chart uses.

Measure yourself right before you order, not months in advance. Body measurements can shift with weight changes, hormonal cycles, or even a new workout routine. A fresh measurement takes two minutes and dramatically reduces the chance of a wrong size.

• Keep the tape parallel to the floor for bust and hips.
• Don't pull the tape tight—snug is enough.
• If your bust and hip measurements fall into different sizes, choose the size that fits your bust for tops and your hips for bottoms.

Read the size chart like a pro

Every brand's size chart is different, so ignore the size you wear at your favorite clothing store. Compare your measurements to the chart's numbers, and look for any notes about fit—some brands run small or large. If the chart lists a range, like 34-36 inches for a medium, and your measurement is at the top of the range, consider sizing up.

Pay attention to how the chart is organized. Some charts separate tops and bottoms, which is helpful because your top and bottom sizes may differ. Others give a single size for a set. If you're buying a bikini set, check whether the top and bottom can be ordered in different sizes.

• Screenshot the size chart before you close the tab.
• Check the model's measurements if listed—it gives real-world context.
• When in doubt, contact customer service with your measurements.

Look for adjustable fit features

The more adjustable a piece is, the more forgiving it will be if your size is slightly off. Halter neck straps, tie-side bottoms, and hook-and-eye closures let you customize the fit. For example, a push-up bikini top with halter ties can be tightened or loosened to suit your comfort, while a fixed-band top has no wiggle room.

Fabric also matters. Swimwear with a high percentage of elastane or recycled lining will stretch and recover, hugging your curves without digging in. If a product description mentions 'sculpting panels' or 'curve-hugging silhouette,' that usually means the fabric is designed to smooth and support, which can help if you're between sizes.

• Tie-side bottoms are more adjustable than fixed-band briefs.
• Halter tops let you adjust lift and coverage.
• Look for soft cushions in push-up tops—they add shape without requiring a tighter band.

Decide between sizes with confidence

If you're between sizes, the general rule is to size up for comfort, especially for one-piece swimsuits and high-waisted bottoms. A too-small swimsuit can dig in, restrict movement, and create visible lines. For bikini tops, if you're between cup sizes, choose the larger size if you prefer more coverage, or the smaller size if you want a tighter, more lifted fit—but only if the top has adjustable straps.

For high-waisted bottoms, consider your torso length. If you have a long torso, you may need to size up to avoid the waistband sitting too low. If you have a short torso, your usual size will likely work. Always check the product's fit notes—some brands specify if an item runs small or large.

• Size up for one-pieces if you're between sizes.
• For bikini tops, use adjustable straps to fine-tune the fit.
• High-waisted bottoms: size up if you have a long torso.

Check the return policy and shipping details

Before you click 'buy,' read the return policy. Swimwear often has hygiene restrictions—some brands only accept returns if the protective liner is intact and tags are attached. Knowing this upfront prevents frustration if the size is wrong. Also check whether return shipping is free or if you'll pay for it.

Look at the shipping timeline. If you need the swimsuit for a specific event, make sure it will arrive in time. Some brands offer express shipping, but it's worth confirming. If you're ordering from a brand you haven't tried before, consider buying two sizes and returning the one that doesn't fit—just verify that returns are allowed for multiple items.

• Keep the original packaging and tags until you're sure.
• Try on swimwear over your underwear to keep it return-eligible.
• Check if the brand offers free returns or exchanges.

Decision rules for buying swimwear online

• When you're between sizes: Size up for one-piece swimsuits and high-waisted bottoms. For bikini tops with adjustable straps, you can sometimes stay with your smaller size if you prefer a tighter fit, but sizing up is safer for comfort. Check if the top has halter ties or adjustable straps—if yes, you have more flexibility.
• When your bust and hip measurements differ: Buy the size that fits your bust for tops and the size that fits your hips for bottoms. If the set only comes in one size, prioritize the area where fit matters most to you—usually the bust for support or the hips for coverage. Look for brands that sell tops and bottoms separately.
• When you want lift vs. natural shape: Push-up tops with soft cushions create deep cleavage and lift. Plunge balcony tops enhance natural cleavage without extra padding. Choose based on the look you want, and remember that push-up styles often have adjustable straps for a custom fit. If you're between sizes and want lift, a push-up with adjustable straps is more forgiving.
• When you're shopping a new brand: Measure yourself fresh, compare to the brand's specific size chart, and read the return policy. If returns are free, consider ordering two sizes. If not, contact customer service with your measurements for a recommendation. Never assume your usual size—brand sizing varies widely.

Product details that help you choose the right size

• push up bikini top: This push up bikini top creates a sexy, deep cleavage with soft cushions on the inside of the cups. The top is crafted from recycled fabric with a digital flower print. By printing digitally, we save 50-60 liters of water per meter of fabric. A knotted bow at the center of your décolleté ties the design together in style. The soft cushions provide lift without needing a tight band, so if you're between sizes, you can choose the larger size for comfort and still get the cleavage effect. The recycled fabric has stretch, which helps with fit.
• push up bikini top: Take the lead in the Royal Navy air force blue push-up bikini top. Soft push-up cushions create a deep, irresistible cleavage, while halter neck straps let you tie the perfect fit. Gold-colored ornaments that don't get hot in the sun add a chic nautical finish. Thoughtfully placed pleats and sculpting panels highlight your curves in premium fabric with recycled lining. The halter neck straps are fully adjustable, so you can tighten or loosen the top to suit your comfort. The sculpting panels and recycled lining offer a curve-hugging fit that can accommodate slight size variations.
• plunge balcony bikini top: Shine with the Dorada golden hour plunge balcony bikini top. The flattering plunge balcony fit enhances your natural cleavage, while soft, luxurious microfiber shimmers in a deep golden hue with delicate gold lurex. A flirty knotted bow at the center adds playful charm, and the curve-hugging silhouette ensures a chic, confident look—perfect for the golden hour by the beach or pool. The plunge balcony fit is ideal if you want natural cleavage without push-up padding. The microfiber fabric is soft and stretchy, which can be more forgiving if you're between sizes, but it may not offer as much lift as a push-up style.
• high waist briefs: Channel bold elegance with these black high waist briefs from the Rebel in lace collection. Crafted from black floral lace, the flattering high waist fit embraces your curves while creating a sculpting silhouette. Playful ruffles add a flirty twist to the semi-sheer design, delivering dramatic, seductive lingerie by marlies|dekkers—crafted with premium materials and designed from a feminine point of view. The high waist fit provides coverage and a sculpting effect, which can help if you're between sizes and want a secure feel. The lace has some stretch, but if you're between sizes, consider sizing up for comfort.

Who this swimwear sizing guide is for

Best for

• Shoppers buying swimwear online for the first time
• Anyone who has received the wrong size from an online order
• People whose bust and hip measurements fall into different sizes
• Shoppers looking for adjustable bikini tops and bottoms

Not for

• Shoppers who can try on swimwear in person before buying
• Those looking for custom-made swimwear
• People who prefer to rely solely on dress size without measuring

Shopping for swimwear online gets much easier when you measure yourself, read the size chart, and choose styles with adjustable features. Keep your measurements handy, check the return policy, and don't be afraid to size up for comfort. With these decision rules, you can order with confidence and enjoy a swimsuit that fits well from the first wear.