If you have ever loved the print and hated the fit, you are not alone. I did the same dance, order two sizes, return one, still fuss with the straps. Here is what fixed it. I measured underbust, bust, and hips once, ran them through a swimsuit size calculator and our swimsuit size chart, then picked a style for the day I actually have, lift, lounge, or laps.
Measure underbust snug, bust over the fullest point, hips at the widest point. Map those to the swimsuit size chart, then pick a top for your goal, balconette for lift, triangle for lounge, cross back for laps. If you land between sizes, use a sister size on the top, keep the bottom true to hips.
Swimsuit Size Calculator
Find your perfect swimsuit size and style recommendations based on your measurements and support preferences. Get personalized suggestions for triangle, balconette, or one-piece styles.
How to measure for swimwear
Underbust Measurement
- Step 1: Wrap measuring tape around your ribcage just under your bust
- Step 2: Keep the tape snug but not tight
- Step 3: Take the measurement in inches
Hip Measurement
- Step 1: Measure around the fullest part of your hips
- Step 2: Keep tape parallel to the floor
- Step 3: Don't pull tape too tight
Swimsuit style guide
- Triangle Bikini: Best for A-B cups, minimal support, most flexible
- Balconette Bikini: Great for C-D cups, underwire support, flattering shape
- One Piece: Maximum support and coverage, ideal for all cup sizes
- High-Waisted: Tummy control and vintage styling
- Tankini: Two-piece convenience with one-piece coverage
How the Swimsuit Size Chart and Support Picker works
Your inputs, bra size, underbust, hips, tummy control
- Bra size and underbust shape cup volume and band tension.
- Hips drive bottom size and one piece ease.
- Tummy control preference selects lining strength, none, light, firm.
What I learned: Cup volume without band tension felt wobbly in water. Now I weigh both.
What you get, size, style, support score
- Sizes: Separate top and bottom, plus one piece.
- Style pick: Triangle, balconette, longline, halter, racerback, one piece, high waist bottom.
- Support score: 0 to 100. Under 30 lounge. 31 to 60 all day swim. 61 to 100 active hold.
Measure once, convert cleanly
Underbust and bust for cup volume
- Tape under the bust, snug and level. Write underbust in inches.
- Tape over the fullest bust point without squashing. Write bust in inches.
- Cup difference guide: 1 inch A, 2 inches B, 3 inches C, 4 inches D, 5 inches DD or E, 6 inches F.
Tiny miss: I measured in a sports bra and lost an inch. Now I use a thin, unpadded bra or no bra.
Hips for bottoms and one piece
- Feet together.
- Tape around the fullest hip and seat.
- That number sets bottom size and one piece comfort through the torso.
Sister sizes for swim tops, plus a worked example
If the cup fits but the band bites, use a sister size.
- Down band, up cup, 34D → 32DD.
- Up band, down cup, 34D → 36C.
Use this for tops only. Keep bottoms true to hips.
Worked example: Underbust 33 in, bust 37 in gives about 34D. Hips 41 in gives Large bottom. I start with a 34D balconette. If the back band floats, I switch to 32DD in the same top. Bottom stays Large.
If you shop across regions, use a swimsuit sizes conversion chart or our International Size Converter before you compare brand charts. If you prefer a guided flow, our step by step works like a simple swimsuit size calculator.
Style guide by goal
Lift, balconette and longline
Why it helps: Underwire and a wider band spread weight, so straps stop digging once you are wet.
What to try: Start at your true bra size. If the back floats, drop the band and raise the cup, 34D to 32DD.
Quick check: Underwire, wider straps, back clasp, optional longline.
My miss: I chose narrow straps and they cut in by noon. Wider straps fixed it without changing size.
Lounge, triangle and bralette
Why it helps: Soft cups and easy ties for sun and short dips.
What to try: Fit the underbust first. If cups float, tighten the tie before moving up a size.
Quick check: Adjustable ties, removable cups, double layer fabric.
Note: I once sized up for coverage and got side gaping. I stayed in the same size and picked a triangle with more side fabric instead.
Laps, racerback and cross back
Why swimmers like it: Straps cross or lock and pull weight to your back, not your neck.
Set it up: Stay true to band. For D and up, choose a higher center front so things stay put on turns.
Quick check: Cross back straps, firm elastic at the ribs.
Pool day: I kept yanking a halter between laps. Cross back and I forgot about it.
Smoothing, one piece and high waist bottom
Why it helps: Power mesh panels smooth without strangling your midsection.
What to try: Pick your hip size first. Choose light mesh for comfort, firm for sharper lines.
Quick check: Lined front, medium or high leg opening so the suit does not cut in.
Lesson learned: I sized up for tummy control and lost hold at the bust. Back to true hip size with firm mesh looked cleaner and stayed put.
The support score, in plain English
Think of it like points for structure. A clasped band beats a pull on. Cross back beats a simple tie. Power mesh adds hold you can feel.
- Band: pull on 5, clasp 10, longline 15
- Cups: unlined 5, lined 10, molded or underwire 20
- Straps: spaghetti 5, standard adjustable 10, cross back 15
- Center: plunge 5, mid 10, high 15
- Fabric: single 5, double 10, power mesh 15
A longline balconette with underwire and mesh lands near 70. A soft triangle with ties sits near 25.
Worried a balconette feels stiff, pick unlined underwire for a lighter feel.
Mix and match rules that save returns
- Top follows underbust and cup.
- Bottom follows hips.
- One piece follows hips, then check torso length.
- Between sizes, set bottom by hips, then use a sister size on the top.
- Halter loads the neck. Cross back spreads the work.
Fit notes for special cases
- Long torso: Prioritize torso length in one pieces or pick a two piece.
- Nursing: Cross front styles or clips help without changing size.
- Post surgery: Look for pockets for inserts, higher centers, and soft linings.
- Plus sizes: Secure the band first, then adjust cup with sister sizes. Avoid upsizing bottoms if hips already fit.
Who this is for, How I tested this, Why it works
- Who this is for: Anyone who wants a suit that stays put in real water, not just a mirror.
- How I tested this: I logged underbust, cup, and hips for three friends and myself over a month of pool days. We tried triangle, balconette, cross back, one piece, and high waist bottoms. I noted strap slip, roll down, and comfort after an hour.
- Why it works: Cup volume plus band tension predict top stability. Hips predict bottom comfort. Mesh and strap geometry add measurable hold, which the score captures.
Fit insurance: If returns are free, order two tops and one bottom on your first try. Return the miss. It costs a label, not a beach day.
Key takeaways
- Start with underbust, bust, and hips, not guesswork.
- Use a swimsuit size chart and adjust with sister sizes on the top only.
- Pick style for your day, lift, lounge, laps, smoothing.
- Choose light or firm mesh, do not size up for tummy control.
- Cross back spreads load better than a halter on long days.
FAQs
Do I size up for tummy control?
No. Choose your hip size, then pick light or firm mesh. Sizing up often creates bust gaping.
What top works best for larger cups?
Balconette or longline with underwire and wider straps. Cross back if you plan to swim laps.
Can I mix sizes?
Yes. Most brands sell separates. Match top to underbust and cup, match bottom to hips.
Triangle tops never work for me, any fix?
Tighten the underbust first, then pick a triangle with more side coverage. If you still fight it, try a longline balconette or cross back.
How do I convert sizes across regions?
Use a swimsuit sizes conversion chart or the International Size Converter to map US, UK, and EU before you check the brand page.
More sizing tools
- Bra Size and Sister Size Finder, confirm your band and cup before picking a swim top
- Balconette vs Plunge, see shapes and coverage at a glance
- International Size Converter, quick US, UK, EU mapping for brand charts
- Shoe Size Converter with Fit Notes, keep the sizing momentum going
- Tools hub, browse all calculators and fit tools
- Ring Size Finder and Calculator, measure at home and convert to US and UK
- Jeans Fit Calculator, find your waist, rise, and inseam
- Cost Per Wear Calculator, buy fewer pieces that earn their keep
- About the Author
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Iskra Banović is our seasoned Editor-in-Chief at Blufashion. She has been steering the website’s content and editorial direction since 2018. With a rich background in fashion design, Iskra’s expertise spans across fashion, interior design, beauty, lifestyle, travel, and culture.
