You've found the perfect thong bikini online. The color is right, the style is everything — and then you freeze. What size do I order? Size anxiety is the #1 reason shoppers abandon their carts, and it's entirely solvable with a tape measure and two minutes of your time.
This guide walks you through exactly how to measure yourself, how to read a bikini sizing chart, and how to choose between sizes when you're on the line. No more guessing. No more awkward returns. Just a thong bikini that fits like it was made for you.
Step 1: Take Three Measurements
All you need is a flexible measuring tape (or a piece of string + ruler). Measure in your underwear or nude for the most accurate results.
Bust
Wrap the tape around the fullest part of your chest, keeping it parallel to the floor. Don't hold your breath — measure at a natural inhale. This number determines your bikini top size.
Waist
Measure around your natural waist — the narrowest point of your torso, usually about an inch above your belly button. This is your bikini bottom reference for high-waist styles.
Hips
Stand with your feet together and wrap the tape around the fullest part of your hips and seat, typically 7–9 inches below your natural waist. This is the most important measurement for thong bikini bottoms.
Write these down. You'll use them every time you shop for swimwear, and they change less than you think from season to season.
Step 2: Read the Sizing Chart
Most swimwear brands — including Audi Swim — size their bikinis in XS through XL (or 2 through 14 in numeric sizing). Here's what those letters generally correspond to:
- XS (2–4): Bust 32–33", Waist 24–25", Hips 34–35"
- S (4–6): Bust 34–35", Waist 26–27", Hips 36–37"
- M (6–8): Bust 36–37", Waist 28–29", Hips 38–39"
- L (8–10): Bust 38–39", Waist 30–31", Hips 40–41"
- XL (10–12): Bust 40–41", Waist 32–33", Hips 42–43"
These are general guidelines. Always check the specific brand's chart, because fit varies based on fabric stretch, construction, and whether the top is adjustable (like a tie-string triangle) or structured (like an underwire bra-style top).
The Bow Babe Triangle Top ($17.99) is fully adjustable at both the neck and back — meaning if you're between sizes, you can dial in the fit with the ties rather than agonizing over XS vs S.
Step 3: Size Your Thong Bikini Bottoms Like a Pro
This is where most people get tripped up. Thong bikini bottoms fit differently than regular underwear or boyshorts — and that's a feature, not a bug.
The Hip Measurement Is Your North Star
Unlike underwear, which is often sized by waist, thong bikini bottoms are sized primarily by hip circumference. Your hip measurement should fall within (or close to) the size range on the chart. If your hips are larger than the upper limit for a given size, size up — a too-tight thong cuts in and creates unflattering lines, while a slightly-loose one can often be adjusted with the side ties.
Check Whether the Bottoms Have Side Ties
Tie-side thong bottoms — like the Bow Babe Contrast Bottoms in Black ($17.99) — are significantly more forgiving than fixed-waistband bottoms. If you're between a S and M, tie-sides let you customize the fit to your exact hip. The bow ties at the hips are both functional and flattering — they add a style detail while solving the between-sizes dilemma.
What About Rise?
Thong bottoms come in three general rises:
- Low rise: Sits 2–3 inches below the natural waist. Elongates the torso, great for shorter torsos and high-hip body types.
- Mid rise: Sits at or just above the hip bone. The most universally flattering rise — hits the widest part of the hip for a smooth silhouette.
- High rise: Sits at or above the natural waist. Cinches the midsection, great for taller frames and those who want more waist coverage without losing the cheeky back detail.
Not sure which rise works for your body type? Our Thong Bikini Bottoms Fit Guide breaks down exactly which rise flatters every body type — it's the perfect companion to this sizing guide.
Step 4: Sizing Your Bikini Top
Triangle tops and bandeau tops size differently from structured styles. Here's the breakdown:
Triangle Tops
Triangle tops like the Bow Babe are sized by band/cup equivalent, but because they're adjustable — you tie the neck and back — fit is mostly about coverage preference and breast fullness rather than strict sizing. A general guide:
- Small bust (32A–34B): XS–S gives great coverage; you can always tie tighter for minimal coverage.
- Medium bust (34C–36C): S–M. Tie the back at full length for support; adjust the neck tie for coverage preference.
- Fuller bust (36D+): M–L. Look for triangle tops with a wider triangle panel and removable pads — the Bow Babe top includes pads you can remove for a sleeker look or leave in for shaping and lift.
The golden rule: if you're between two sizes, size up for tops. You can always tie a slightly larger triangle tighter. A too-small top across a fuller bust creates spillage and discomfort.
Bandeau and Bralette Styles
These size more like bralettes. Your underbust measurement (snug around your ribcage) is the key — it determines band fit. Cup sizing is typically soft-cup, with most bandeau styles fitting A–C cups comfortably; D+ cups generally need more support from thicker straps or underwire.
What to Do When You're Between Sizes
You're a 37" hip — right between S (max 37") and M (min 38"). Here's how to decide:
- Go up for bottoms. The discomfort from a too-tight thong bottom is immediate. Size up and use the tie to cinch if needed.
- Match your fuller measurement for tops. If your bust fits S but your hips are M, buy S tops and M bottoms. Mixing sizes is normal — and expected.
- Choose stretchy fabrics. Audi Swim's proprietary Luxe-Flex nylon-spandex blend is engineered to stretch and recover, conforming to your exact shape rather than forcing you into a rigid size box. It's why customers find they can wear the same size across a 2–3 lb weight fluctuation.
- Consider sustainable fabric properties. The Bow Babe Collection is available in ECONYL recycled nylon — not only better for the ocean, but also known for exceptional stretch retention that keeps its shape season after season.
Complete the Look: Your Perfectly-Sized Set
Once you know your measurements, building your ideal Audi Swim look takes about 90 seconds. The Bow Babe Collection is available in three colorways — all with adjustable construction that plays nice with between-size bodies:
- Top (your size): Bow Babe Top - Black ($17.99) / Pink ($17.99) / Sky Blue ($17.99)
- Bottoms (your size, or one up): Bow Babe Bottoms - Black ($17.99) / Pink ($17.99) / Sky Blue ($17.99)
- Cover-up: Beach Muse Crochet Dress ($29.99)
- Accessory: Golden Hour Belly Chain ($12.99)
Full set total: $78.96 — versus $150–300+ for a comparable designer thong bikini set. Size anxiety solved. Cart abandoned? Never again.
Already know your size but want to explore more cut options? The Complete Guide to Bikinis for Every Body Shape pairs perfectly with this sizing guide — once you know your measurements, you can choose the cut that flatters your specific proportions. Considering a thong for the first time? The Honest Guide to Your First Thong Bikini covers exactly what to expect.
Want to explore all styles and sizes? Browse the full Thong Bikini Collection and the complete Audi Swim collection — all sizes in stock now.
Frequently Asked Questions
Should I size up or down if I'm between thong bikini sizes?
For bottoms, always size up. A thong that's too tight creates discomfort and unflattering lines at the hip. A slightly larger bottom with tie sides can be adjusted to fit your exact hip. For tops, if you're between sizes and have a fuller chest, size up for better coverage and comfort. Triangle tops with adjustable ties (like the Bow Babe Top, $17.99) can always be tightened to fit a smaller frame.
Can I wear different top and bottom sizes in a bikini set?
Absolutely — and most women do. Your top size is driven by your bust; your bottom size by your hips. These measurements are often different. If you're a S on top and M on bottom, buy accordingly. All Audi Swim bikini tops and bottoms are sold separately, making mix-and-match sizing effortless.
How do I know if a thong bikini fits correctly?
A well-fitting thong bikini should lie flat against your skin without digging in or gaping. The front panel should cover your desired coverage zone without pulling or bunching. The strings should sit comfortably at your hip — snug enough not to slide, loose enough that you can slip two fingers underneath. For tops, the cups should contain your bust with no spillage, and the band should sit parallel to the floor across your back. If the fabric is rolling or folding anywhere, size up. The Thong Bikini Fit Guide has a full visual breakdown of what proper fit looks like for every style.
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