Best Bikinis by Style: String, Triangle, Bandeau, Underwire and High-Waisted Compared

Pick a bikini by how much band it has. Support comes from the band, so the less band a style has, the smaller the cup it suits. That rule is the short answer for anyone searching for the best bikinis by style. String tops suit A and small B cups, triangle tops A to C, and a boned bandeau can reach a D. Above that, buy an underwire top sold in a cup range that includes yours.

How this review was done

This is a desk review. Every cup range below comes from a brand’s own fit guide or product page. Nobody wore, swam in, or washed these suits for this piece. Where a brand does not publish a figure, we say “not published” rather than estimate one. For brands ranked on fit and size range, see our bikini brands comparison.

Types of bikinis compared

Cup ranges in this table are brand-stated, taken from Monday Swimwear’s fit guide. The support, failure, and best-for columns are editorial judgment based on each style’s construction.

Style	Where support comes from	Cup range it suits (published example)	Main failure	Best for
String	Neck and back ties only	No string top with a published cup range found	Cups slide off center	A and small B cups, lounging
Triangle	Ties, sometimes a thin underbust string	Monday Taormina Top: A to C	Side gaping above a C	A to C cups, light swimming
Bandeau	A firm band and side boning, no straps	Monday St. Martinique Bandeau: A to D	Slides down when wet	A to D cups, no strap lines
Underwire	Wire and band together	Monday Sorrento Top: A to G	Wire digs if band or cup is wrong	D cups and up, active swimming
Halter or balconette	Band and wire, with straps adding lift	Monday Honolulu Top: A to E	Neck strain from a loose band	Lift at C to E
High-waisted bottom	Waistband at the natural waist	Bottoms carry a size range, not a cup rating	Rolls down on a long torso	Midriff coverage, mixed sizes
Tankini	Whatever band sits under the tank	No confirmed example: not published	Hem floats up in the water	Coverage over support

String bikini

What it is: Wikipedia’s Bikini variants article describes the string bikini as a scantier cut than a regular bikini. In practice that means small triangle cups on thin ties, with tie-side bottoms.

How it holds: A string top holds very little, and that is by design. The back string supplies most of the tension and the neck tie supplies the rest. The University of Portsmouth’s Research Group in Breast Health states that straps “are not the main support.” The band is, and it should sit level and firm. A string top has no firm band and no structured cup, so its hold depends on how tight you tie it.

Who it suits: A and small B cups who want minimal tan lines and plan to lounge.

Who it does not: Anyone above a B cup, anyone who dives or surfs, and anyone bothered by a knot at the nape.

Example: none of the brand pages in this review gave a string top with a published cup range. That absence is the finding: brands rarely rate string tops by cup, so treat them as A and small B styles unless a brand says otherwise.

Triangle bikini

What it is: Two triangular cups joined at the center, on a neck tie, with a back tie or a thin band underneath. The cups are usually larger and more often lined than on a string top.

How it holds: The underbust string gives the top some anchor, but it is narrow. Most of the shaping comes from cup fabric pulling across the breast. Once the bust outgrows the triangle, the cup edges pull inward and gape at the sides.

Who it suits: A to C cups who want a classic shape for lounging and light swimming.

Who it does not: Full busts on narrow backs, because the cups have nothing structured to anchor to.

Example: Monday’s Taormina Top, which its fit guide describes as a “Skimpy Triangle top” with thin straps and adjustable ties, is rated A to C. That matches the rule: a triangle with no firm band suits the smaller cups.

Bandeau bikini

What it is: Wikipedia defines it as “a bandeau top, with no straps.” A tube of fabric wraps the bust and ribcage.

How it holds: A bandeau is almost all band, which is why it can hold more than it looks like it should. With no straps, the band grips the ribcage with no help from above. Side boning stops the fabric rolling, and a center wire or seam separates the cups.

Who it suits: A to D cups who want no strap lines, as long as the band is firm.

Who it does not: Cups above a D, lap swimmers, and anyone who jumps off boats.

Example: Monday’s St. Martinique Bandeau is rated A to D. It has side boning, a U-wire detail, and a removable halter strap for days when the band needs help. The Tamarama Top is also rated A to D, but lists only an adjustable back tie, with no strap or boning. Fit can vary from style to style, so check Monday’s size chart and any product-specific fit notes before choosing a size.

One warning if a brand suggests sizing up a bandeau: sizing up loosens the band, the one part a bandeau cannot afford to lose. Size up for the cups, then tighten the back tie. For a D cup, the St. Martinique is the safer of the two because of the boning and strap option.

Underwire bikini top

What it is: An underwire bikini top is a bra built in swim fabric. It has a wire under each cup, a band, and usually shoulder straps.

How it holds: The wire stiffens the base of each cup. That spreads the band’s tension around the breast instead of flattening it. Underwire is the first style on this list where cup volume can scale up without losing hold.

Who it suits: D cups and above, and anyone who swims hard and wants a top that stays put without retying.

Who it does not: Small cups that dislike structure, and anyone whose band and cup fall outside the brand’s grid.

Example: Monday’s Sorrento Top is an underwire top rated A to G in its fit guide, and its Capri Top, also underwired, is rated A to DDD. Monday sizes its tops in nine letter sizes, PP to VVV, each with bust and underbust measurements. Its cup range is a per-style rating, not a size you order.

Bra-sized brands sell by band and cup instead. Per Aerie’s own size listings, its bikini tops run from 30A to 38DD. Freya sells bra-sized DD+ swim with bands from 28, according to its size listings. Fantasie’s swim sizing runs bands 30 to 44 and cups D to J in UK letters. If your band is under 30 or your cup is past G, a bra-sized specialist is a better bet than a letter-sized brand. Our guide to underwire bikini tops for DD+ compares them.

Balconette or halter bikini

What it is: Both styles are variants of the underwire top. A balconette cuts the cup lower and sets the straps wider, so it lifts from below. A halter replaces the two shoulder straps with one strap or tie behind the neck.

How it holds: Band and wire still do the work. A halter adds upward pull from the neck. That feels secure, but it moves load onto the neck when the band is loose. If a halter always seems to need tightening, the band is usually a size too big.

Who it suits: C to E cups who want lift and a centered shape. Halters also suit sloping shoulders where straps slip.

Who it does not: Anyone prone to neck ache, and cups past E in a halter-only fastening. Choose a balconette with shoulder straps instead.

Example: Monday’s Honolulu Top, an underwire top with an adjustable halter neck and back tie, is rated A to E in its fit guide. We did not find a balconette with a published cup range.

High-waisted bikini bottoms

What it is: A bottom with a waistband at or near the natural waist, often with a high-cut leg.

How it holds: The waistband grips the narrowest part of the torso, and the leg openings stop it twisting. It has no effect on top support. Because it is a separate piece, you can buy top and bottom in different sizes.

Who it suits: Readers who want midriff coverage, or whose bust and hips take different sizes.

Who it does not: Long torsos, where the band lands below the waist and rolls. Very short torsos can see it bunch under the bust. Compare the brand’s waist measurement with your own before ordering.

Example: bottoms carry no cup rating. Monday’s fit guide lists a size range for each bottom instead, and individual styles do not always cover the full PP to VVV run, so check the specific style’s chart before ordering.

Tankini

What it is: Wikipedia describes a tankini as a tank top combined with a bikini bottom.

How it holds: The tank’s length adds coverage, not support. Support comes from whatever sits underneath, such as a shelf band, molded cups, or full underwire. A tankini with no inner band is a tank top over an unsupported bust.

Who it suits: Readers who want stomach coverage with the flexibility of separates.

Who it does not: Lap swimmers, because the hem floats up in the water.

Example: We have no example to name, because none of the brand pages in this desk review gave a tankini with a published cup range. Above a D cup, look to bra-sized specialists and confirm that the listing gives a band size.

What goes wrong, why, and the fix

• The back rides up. The band is too loose, often because you sized up for the cups. Go down a band and up a cup, or tighten the tie.
• The bandeau slides down after a swim. Wet fabric gets heavier and loses grip. Choose boning or a convertible strap.
• Triangle cups gape at the sides. The bust has outgrown the style. Move to an underwire.
• The wire digs under the arm. The cup is too small. Go up a cup and keep the band.

Black and white bikinis: color and opacity

Black is the safe color for opacity. White and ivory are the risky ones, because wet fabric lets light through and pale fabric shows what is behind it.

Light shades like ivory are the ones most likely to turn sheer when wet, and a lining does not always fully prevent it. Monday’s own Clovelly One Piece page says that “ivory is a soft hue that some have found to be sheer when wet.” We count it as a credit to any brand that prints that kind of information plainly.

Extra lining does not fix the problem on its own. Swim fabric supplier Sportek reports that two layers of white lining block less light than one layer of beige, so lining color matters more than layer count. For a white bikini, look for a skin-tone lining in the product details. If the page says “lined” but names no lining color, ask the brand, or choose a darker shade. Our swimwear fabric guide covers fabric weight and lining in more depth.

FAQ

What is the best bikini style for a large bust?

The best style is an underwire top with a firm band and shoulder straps. The wire and band carry the weight, so the top holds without relying on ties. Above a G cup, or on a band under 30, a bra-sized specialist will usually stock your size where a letter-sized brand will not.

Which bikini style stays on best for swimming?

An underwire top with shoulder straps and a back closure stays on best. It anchors at the band and at the shoulders, so a dive or a wave has less to pull loose. String and strapless bandeau tops are the least secure in the water.

Can a bandeau work for a D cup?

Yes, if it has side boning and a strap option. The boning stops the band rolling, and the strap takes over when wet fabric loses grip. A bandeau held by a back tie alone is a riskier buy at a D.

Should I buy my bikini top and bottom in the same size?

Only if both measurements land in the same row of the size chart. Separates exist so you do not have to compromise. Size the top by bust and underbust and the bottom by waist and hip.

Are triangle bikinis good for small busts?

Yes, they suit A to C cups well. The cups have less fabric to fill, so they lie flat rather than gaping. Removable padding adds shape if you want it.

Before you order

Every cup range in this guide is only useful if you know your own numbers. Measure your underbust, bust, waist, and hip before you compare charts, then match each figure to the style you have chosen. Our guide on how to measure for swimwear walks through each measurement.