Size Guide
Train One Piece Swimsuits
Torso measurement is most important for finding your accurate one piece size.
If you are in between torso measurements or know your torso runs long we recommend sizing up!
Excludes Caroline & Rylee One Piece Swimsuit.
Caroline & Rylee One Piece Swimsuit
Surf One Piece Swimsuits
Wait, what's the difference?
Great question. It's confusing—we know!
Train swimsuits are made with super compressive, chlorine-proof fabric designed for athletes who demand durability, comfort, and peak performance during high-impact sports, hour-by-hour training in the pool, or long distance swims out in the ocean.
The Caroline One Piece Swimsuit is part of our Train line, but the silhouette fits differently! If you're unsure, use the dress size column in the size chart to find your best fit.
Surf swimsuits are made with a more flexible fabric that still holds everything in place but isn't as compressive. These are ideal for recreational adventures—less intense, more laid-back.
TLDR:
Train = performance mode.
Surf = play mode.
HOW TO MEASURE
Torso
The most important for finding your accurate one piece size
Measure from the top of your shoulder over the fullest part of your bust, through your legs and around, up your back to the starting point.
If you are in between torse measurements or know your torso runs long, we recommend sizing up!
Bust
Measure around the fullest part at the bust.
Waist
Measure around the smallest part of the waist.
Hips
Keep measuring tape parallel to the floor and measure around the fullest part of the hip.
Train Bikini Tops
To find your bust measurement - measure the circumference of fullest part of your chest.
Surf Bikini Tops
Wait, what's the difference?
Great question. It's confusing—we know!
Train swimsuits are made with super compressive, chlorine-proof fabric designed for athletes who demand durability, comfort, and peak performance during high-impact sports, hour-by-hour training in the pool, or long distance swims out in the ocean.
Surf swimsuits are made with a more flexible fabric that still holds everything in place but isn't as compressive. These are ideal for recreational adventures—less intense, more laid-back.
TLDR:
Train = performance mode.
Surf = play mode.
HOW TO MEASURE
Torso
The most important for finding your accurate one piece size
Measure from the top of your shoulder over the fullest part of your bust, through your legs and around, up your back to the starting point.
If you are in between torse measurements or know your torso runs long, we recommend sizing up!
Bust
Measure around the fullest part at the bust.
Waist
Measure around the smallest part of the waist.
Hips
Keep measuring tape parallel to the floor and measure around the fullest part of the hip.
Train Bikini Bottoms
Surf Bikini Bottoms
Wait, what's the difference?
Great question. It's confusing—we know!
Train swimsuits are made with super compressive, chlorine-proof fabric designed for athletes who demand durability, comfort, and peak performance during high-impact sports, hour-by-hour training in the pool, or long distance swims out in the ocean.
Surf swimsuits are made with a more flexible fabric that still holds everything in place but isn't as compressive. These are ideal for recreational adventures—less intense, more laid-back.
TLDR:
Train = performance mode.
Surf = play mode.
HOW TO MEASURE
Torso
The most important for finding your accurate one piece size
Measure from the top of your shoulder over the fullest part of your bust, through your legs and around, up your back to the starting point.
If you are in between torse measurements or know your torso runs long, we recommend sizing up!
Bust
Measure around the fullest part at the bust.
Waist
Measure around the smallest part of the waist.
Hips
Keep measuring tape parallel to the floor and measure around the fullest part of the hip.
HOW TO MEASURE
Bust
Measure around the fullest part of your bust.
Underband
Measure around your ribcage directly under your bust—make sure the tape measure is snug and parallel to the floor.
Waist
Measure around the smallest part of your waist.
Hips
Keep the measuring tape parallel to the floor and measure around the fullest part of your hips.
HOW TO MEASURE
Bust
Measure around the fullest part of your bust.
Underband
Measure around your ribcage directly under your bust—make sure the tape measure is snug and parallel to the floor.
Waist
Measure around the smallest part of your waist.
Hips
Keep the measuring tape parallel to the floor and measure around the fullest part of your hips.
Active Bottoms
Excludes the Lizzie Split Short, Rory Short and Anna Tight Short.
Lizzie Split Short, Rory Short and Anna Tight Short
HOW TO MEASURE
Torso
The most important for finding your accurate one piece size
Measure from the top of your shoulder over the fullest part of your bust, through your legs and around, up your back to the starting point.
If you are in between torse measurements or know your torso runs long, we recommend sizing up!
Bust
Measure around the fullest part at the bust.
Waist
Measure around the smallest part of the waist.
Hips
Keep measuring tape parallel to the floor and measure around the fullest part of the hip.
WATCH OUR GUIDE VIDEO
Fabric Fit Tip!
Different fabrics can make a difference in how your suit fits. Check out our fabric guide below to learn more.
Swimsuit Fabrics
| SplashTec | Foreverever | Recycled SurfTec | Recycled Sea-Flex | |
|---|---|---|---|---|
| Best For | Entry-level Swimmers | High-impact Training | High-impact Recreational Activities | Recreational Activities |
| Chlorine Proof | 150 hours | 150 hours | ||
| Sizing | Fits True to Size | Size Up (recommended) | Fits True to Size | Fits True to Size |
| Stretch Level | ||||
| Handfeel | Soft, stretchy, durable | Soft, sturdy, durable | Soft, stretchy, comfortable | Soft, stretchy, comfortable |
| UPF 50+ | ||||
| Shop All | Shop All | Shop All | Shop All | |
Train Swim Briefs
Train Swim Jammer
HOW TO MEASURE
Thigh
Stand straight and measure from the highest point of your inner thigh down towards your knee.
Inseam
Wrap a measuring tape around the widest part of your thigh, ensuring it's snug but not too tight.
FAQ
I need more help!
That's what we're here for! Shoot us an email at contact@jolyn.com, and our team will help you figure out the best size, style, or anything else you need.
How do I know if I'm between sizes?
If you're between sizes, we suggest sizing up for a more comfortable fit or down for a more snug, athletic feel. And don't forget to check the fit notes on each product page—they're super helpful.
Do JOLYN swimsuits fit true to size?
JOLYN swimsuits are designed for performance, so they fit tighter than typical fashion swimwear. They should feel secure and supportive without restricting your movement.
What's the difference between JOLYN Train and Surf fabrics?
Our Foreverever™ fabric (used in Train suits) is super compressive and made for serious swimming, water polo, and diving. SurfTec and Sea-Flex (used in Surf suits) are softer, stretchier, and perfect for ocean lifeguarding, surfing, or just splashing around.
Which JOLYN styles are best for larger busts?
For more support and coverage, look for styles with thicker straps or built-in support. Some customer faves: the Caroline One Piece, Kathleen Bikini Top, and Ruth Bikini Top.
I'm new to competitive swimming and don't know where to start!
Welcome to the squad! We recommend the Marie or Tabitha One Piece. They're comfy, full-coverage, come in sizes 18–38, and are a great intro to training suits (plus they're only $58).
What is your return policy?
We accept returns within 30 days for a refund or 45 days for store credit on eligible items. Please note: Final Sale items are non-returnable.
