Finding a bikini that fits well can make all the difference. The right size feels comfortable, stays in place and flatters your shape, while the wrong size can dig in, gape or leave you constantly adjusting.
Because swimwear is designed to fit closely to the body, sizing can feel a little trickier than everyday clothing. The good news is that a few simple measurements and fit checks can help you choose with confidence.
This guide covers how to measure yourself for a bikini, how a bikini top and bottoms should fit, what to do if you are between sizes, and how to convert between UK, US, EU and AUS sizes.
How to Measure Yourself for a Bikini
Use a soft tape measure and measure over your underwear or bare skin. Keep the tape level and snug, but not tight.
- Full bust: measure around the fullest part of your bust.
- Waist: measure around the smallest part of your waist.
- High hip: measure 3 to 4 inches below your waist, along your hip bones.
Your full bust measurement guides your bikini top size, while your high hip measurement guides your bikini bottom size. Compare your measurements to the chart below to find your size.
Bikini Size Chart
| AB Size | Full Bust | Waist | High Hip |
|---|---|---|---|
| XS | 30–32" | 22–24" | 32–34" |
| S | 32–34" | 24–26" | 34–36" |
| M | 34–36" | 26–28" | 36–38" |
| L | 36–38" | 28–30" | 38–40" |
| XL | 38–40" | 30–32" | 40–42" |
| 2XL | 40–42" | 32–34" | 42–44" |
UK, US, EU and AUS Bikini Size Conversions
Swimwear sizes vary between countries, so it helps to know how sizes compare. Use this table as a general guide, but always check your own measurements first, as they are the most accurate way to find your size.
| AB Size | UK | AUS/NZ | US | EU |
|---|---|---|---|---|
| XS | 4–6 | 4–6 | 0–2 | 32–34 |
| S | 6–8 | 6–8 | 2–4 | 34–36 |
| M | 8–10 | 8–10 | 4–6 | 36–38 |
| L | 10–12 | 10–12 | 6–8 | 38–40 |
| XL | 12–14 | 12–14 | 8–10 | 40–42 |
| 2XL | 14–16 | 14–16 | 10–12 | 42–44 |
For the full size chart and bra size reference, visit the Size Guide.
How Should a Bikini Top Fit?
A well-fitting bikini top should feel secure and comfortable, giving you the coverage you want without needing constant adjustment.
Signs your bikini top fits well
- The cups cover the bust comfortably, without spilling over the sides, top or bottom.
- The fabric lies smoothly against your body without gaping.
- The straps feel secure without digging into your neck, shoulders or back.
- The top stays in place when you move, swim or lie down.
Signs your bikini top is too small
- Your bust spills out of the cups.
- The straps or back band dig in or leave marks.
- The top rides up when you raise your arms.
Signs your bikini top is too big
- The cups gape or wrinkle.
- The top slips down or moves out of place easily.
- The straps need tightening so much that the shape of the top is pulled out of place.
How Should Bikini Bottoms Fit?
Bikini bottoms should sit smoothly on the hips and give you the coverage you are comfortable with, without cutting in or sagging.
Signs your bikini bottoms fit well
- The waistband and leg openings sit flat against your skin without digging in.
- The fabric stays in place when you walk, sit or swim.
- The coverage at the back matches the style you have chosen.
Signs your bikini bottoms are too small
- The sides or leg openings dig into your hips.
- The bottoms feel tight across the hips or ride up uncomfortably.
Signs your bikini bottoms are too big
- The fabric sags or wrinkles, especially when wet.
- The bottoms slip down when you move or swim.
Coverage also depends on the style. To understand how different shapes compare, read the guide to cheeky vs Brazilian bikini bottoms.
Adjustable vs Fixed Bikini Styles
Whether a bikini is adjustable or fixed can make a big difference to how you choose your size.
Adjustable bikinis with tie straps
Many bikini styles feature adjustable tie straps, which means you can be more flexible with the size you choose. Whichever size you go for, you can tie the straps to fit you exactly, tightening or loosening them around your neck and back for a secure, comfortable fit.
Most Ashlea Baker Swimwear designs are adjustable, including classic and ruffle triangle tops. Explore the different styles in the ultimate guide to triangle bikini tops.
Fixed bikini styles
Some bikini pieces have a fixed back or no adjustable straps, so the size you choose needs to be more precise. If you are unsure or between sizes with a fixed style, sizing up is the safer choice. A bikini that is too small can dig in, which is uncomfortable and can be unflattering.
The Cocobay Knotted Bikini Top and White Starfish Bikini Top both have a fixed back, so check your measurements carefully before choosing your size.
What If You Are Between Sizes?
If your measurements fall between two sizes, choosing the larger size is generally recommended for a more comfortable fit.
For adjustable styles with tie straps, you have more flexibility, as the straps can be tied to fit. For fixed styles, sizing up is the safer option to avoid the fabric digging in.
What If You Are a Different Size on Top and Bottom?
This is very common, as many women are a different size on their top half and bottom half.
Every Ashlea Baker Swimwear bikini top and bikini bottom is sold separately, so you can choose the right size for each. Simply use your full bust measurement to choose your top size, and your high hip measurement to choose your bottom size.
Bikini Sizing for Fuller Busts
Bust measurement alone does not always capture cup volume, so a fuller cup at the same bust measurement can need extra room through the cup itself.
As a general guide, bra sizes with a D cup or above start from size M. For example, a 32DD wears a size M bikini top.
Adjustable straps can help you tailor the fit around your neck and back, but they do not change how much room there is in the cup. If you have a fuller bust, choose your size based on your cup as well as your measurements. If you wear an F cup or above, or your bra size is not listed in the Size Guide, feel free to get in touch before ordering for personal sizing advice.
Bikini Sizing FAQs
Should I size up or down in a bikini?
It depends on the style. With adjustable bikinis that have tie straps, you can be more flexible, as the straps can be tied to fit you exactly. With fixed styles that have no straps to adjust, sizing up is the safer choice if you are unsure or between sizes.
Should a bikini be tight or loose?
A bikini should feel snug and secure, but never so tight that it digs in, as this can be uncomfortable and unflattering. Swim fabric can also relax slightly when wet, so a bikini that already feels loose when dry may not stay in place in the water.
What size bikini am I if I am a UK 10?
A UK 10 usually falls between a size M and a size L, depending on your measurements. Check your full bust and high hip measurements against the size chart to find your best fit. If you are between sizes, choose the larger size for fixed styles.
What is a UK 12 in US bikini sizes?
A UK 12 is usually around a US 8. Sizes can vary slightly between brands, so your own measurements are the most accurate guide.
Is bikini sizing the same as clothing sizing?
Not always. Swimwear fits closer to the body than most clothing, so it is worth measuring yourself rather than relying on your usual dress size.
Finding Your Perfect Bikini Fit
The best bikini is one that fits comfortably, stays in place and gives you the coverage you feel confident in. Take your measurements, check the size chart, and consider whether the style is adjustable or fixed before choosing your size.
For the full size chart and bra size reference, visit the Size Guide. Once you have found your perfect fit, learn how to wash swimwear to keep your bikini looking its best, or browse the full swimwear collection.