A junior tech suit should feel very different from a training costume or pair of jammers. It is designed to compress, support and sit securely through a dive, breakout, turns and the final metres of a race. That is why junior tech suit sizing can feel daunting for swimmers and parents alike: too loose and the suit cannot do its job; too small and getting it on becomes a stressful pre-race battle.
The right fit is not the smallest size a swimmer can eventually squeeze into. It is a suit that delivers purposeful compression while allowing the swimmer to move, breathe and race with confidence. Start with accurate measurements, use the individual brand size chart, and leave enough time before a gala to try the suit on calmly.
Why junior tech suit sizing is different
Tech suits use performance fabrics that are much less forgiving than everyday swimwear. Their construction is intended to create a close, hydrodynamic fit, with fabric and seams positioned to support the body in the water. A junior swimmer who normally wears a certain size in a training suit may therefore need a different size in a racing suit.
There is no universal size conversion between brands, or even between models from the same brand. Arena, Speedo and other leading performance brands each use their own sizing charts, cuts and fabric blends. A higher-compression suit can feel noticeably firmer than an entry-level racing suit in the same labelled size.
This is also why age alone is not a reliable guide. Two 12-year-olds may be the same height but have very different waist, hip, chest or thigh measurements. Always size the swimmer, not the birthday on the box.
Measure first, then use the brand chart
A soft tape measure is the best starting point. Take measurements against the body rather than over clothing, keeping the tape level and snug without pulling it tight. For girls' kneeskin and racing costume styles, the most useful measurements are usually chest, waist, hips and torso loop. The torso loop runs from the shoulder, down through the legs and back up to the same shoulder.
For boys' tech jammers, focus on waist and hips, while checking the relevant chart for thigh guidance where provided. Height can be useful as a sense check, especially for a longer-legged swimmer, but it should not override the main measurements.
Measure before ordering, rather than relying on a costume bought months ago. Junior swimmers grow quickly, and a small change around the hips or torso can alter the best fit. If measurements sit across two sizes, the decision depends on the suit model and the swimmer's build. A more forgiving fabric may suit the lower size, while a very stiff, highly compressive model may be more comfortable and practical in the larger option.
Do not size down for the sake of compression
A common mistake is assuming a tech suit must be painfully tight to be fast. It should be close-fitting, but it should not create sharp discomfort, restrict a full breath or leave deep marks after a brief fitting. If the swimmer cannot move their arms freely, squat comfortably, or settle the suit into position without extreme force, it is probably too small.
Excessive compression can distract a junior swimmer from racing well. It can also increase the risk of damaged fabric, seams or straps while putting the suit on. The aim is a controlled, race-ready feel, not a test of strength in the changing room.
What a correct tech suit fit looks like
Once on, the suit should lie smooth and even across the body. There should be no loose pockets of fabric at the lower back, hips, seat or behind the knees. For girls' suits, check that the straps sit securely without digging in and that the body of the suit reaches its intended position without pulling excessively through the shoulders.
For boys' jammers, the waistband should sit flat and secure, and the legs should finish evenly with no rolling or bunching. The swimmer should be able to stand upright, raise their arms, sit down and move through a few gentle squats without the suit shifting or causing pain.
Wrinkles do not always mean the suit is too large. A suit that has not been fully worked into place can show small creases, particularly around the hips and thighs. Take time to lift and smooth the fabric gradually, moving it into position a small section at a time. Never pull hard on one point, especially around seams, straps or the leg openings.
Allow more time than you think
Putting on a tech suit is part of race preparation, not a two-minute job at poolside. For a first fitting, allow plenty of time at home when the swimmer is relaxed, dry and not rushing to warm up. Dry skin and dry fabric make the process easier. Remove jewellery, keep fingernails smooth, and avoid pulling the suit with fingertips or nails.
Work from the ankles upwards for jammers and kneesuits. Gather a small amount of fabric, ease it over the foot or leg, then release and repeat. Once the suit is over the hips, smooth the fabric upwards rather than trying to drag the top section into place in one movement. This patience helps protect a suit that may be reserved for key meets.
A new tech suit often takes longer to put on than one that has been worn carefully before. That does not automatically mean the sizing is wrong. However, if it requires prolonged force, causes distress or cannot be positioned properly, stop and reassess rather than risking damage.
Choose the suit around the swimmer and the meet
Not every junior needs the most aggressive compression available. A developing swimmer attending their first county event may benefit more from a comfortable, dependable entry-level racing suit than a premium model that feels intimidating or difficult to wear. Confidence on the blocks matters.
The event programme matters too. A swimmer racing a single target event may be happy in a firmer suit, while someone swimming several races across a long session needs a fit they can tolerate comfortably for longer. Some swimmers also prefer a slightly more flexible feel for strokes requiring greater shoulder movement.
Check the rules for the specific competition before purchasing or racing. Requirements can vary by age group, meet level and governing body policy, particularly around approved suits and junior restrictions. Coaches are often a helpful sounding board because they know how a swimmer races, how quickly they are growing and whether a particular suit style is likely to suit them.
Avoid expensive fitting mistakes
Buying well ahead of a major championship can be sensible, but avoid ordering so early that a growth spurt changes the fit before race day. For younger swimmers, it can be practical to measure again closer to the event, especially if the suit has been saved for a season highlight.
Do not use a tech suit as regular training kit. Chlorine exposure, repeated stretching and frequent changing-room use will shorten its competitive life. Keep it for racing or selected race-pace sessions, rinse it gently in cool fresh water after use, and allow it to dry naturally away from direct heat.
Parents should also resist comparing sizes between squad mates. One swimmer may wear a smaller label because of their shape, their preferred model or the brand they have chosen. The successful fit is the one that gives that individual swimmer secure support and freedom to race their own race.
Junior tech suit sizing checklist before race day
Before the first meet, confirm that the swimmer has been measured against the correct brand chart, has tried the suit on without rushing, and can move comfortably through normal poolside motions. Check that there are no loose areas, rolled leg openings, twisting straps or painful pressure points. It is also worth packing the suit carefully and leaving enough time at the venue to put it on properly.
All4Swim customers can shop by swimmer, brand and racewear need, but the sizing decision should always come back to the chart for the exact suit. A well-fitted tech suit should feel purposeful from the moment it is on, then fade into the background when the swimmer steps up to race. That is the real goal: less time worrying about kit, and more attention on the start, the stroke and the swim ahead.