The 2026 THETA sizing guide works on one core principle: tops are cut fitted across the chest and relaxed on the stomach, and shorts use a fitness-racing-specific fit. Take your normal size for a performance fit, size up one for a looser feel, and use the fitted-chest, relaxed-stomach cut to judge how a top will sit rather than a slim or baggy label.
How does THETA cut its tops?
Most people assume a performance top has to be either slim or baggy, and that you pick your side. That is the misconception worth clearing first. Every THETA top follows a single design language instead: fitted across the chest and relaxed over the stomach, with the Race Team v2 tee precision cut per size rather than simply scaled up and down. The fitted chest keeps the top close so it does not flap on the eight runs or catch on the sled harness. The relaxed stomach stops the fabric clinging when you breathe hard or hinge at the hips. So if you like a true performance fit, take your normal size; if you prefer more room through the body, size up one and accept a slightly looser chest. The fabric is ultra-light and does not cling when soaked, so it never needs to be worn tight to perform.
How should the shorts and bottoms fit?
Start with what the shorts are trying to solve. THETA shorts use a fitness-racing-specific fit, which sits closer than a standard loose run short so they stay put through sandbag lunges and burpee broad jumps. The Tech Short v2 pairs that fit with durable polyester and elastane 4-way stretch, so a closer cut never restricts a deep lunge; take your normal size and the stretch does the rest. The half tights are a different fit again, sitting close by design with a sweat-wicking liner and multiple pockets, so again take your normal size for a supportive feel. What is easy to miss is that the closer race short is intentional: loose shorts lose their shape under intensity, while a race fit keeps a clean silhouette when you are fatigued and wet.
| Piece | Fit character | Sizing guidance |
|---|---|---|
| Tech / Race tops | Fitted chest, relaxed stomach | Normal size; size up for looser body |
| Tech Short v2 | Fitness-racing-specific, close | Normal size |
| Half Tight | Close, supportive | Normal size |
| Women's race pieces | Women's engineered fit | Normal size; women's-specific cut |
Why does the fitted-chest, relaxed-stomach cut change how you size?
The reason this cut matters for sizing is that it decouples two things most tops tie together. On a standard slim top, the chest and the stomach are cut to the same tightness, so if you want the chest close enough not to flap on a run, you also get a stomach panel that clings the moment you breathe hard or hinge. That is why people so often size up in performance tops and then complain the whole thing is loose. THETA solves it at the pattern rather than the size: the chest is held close for the run and the harness, and the stomach is already given room, so you do not have to buy a larger size to escape a clinging belly panel.
Once you understand that, the sizing advice stops feeling arbitrary. Take your normal size and you get a chest that stays put and a stomach that was never going to cling in the first place. Size up only if you specifically want the chest looser too, accepting that the top will now flap a little more on the run. The fabric reinforces the logic: it is ultra-light and does not cling when soaked, so there is no performance reason to wear it tight. Tightness in a technical top is usually people trying to stop a clinging stomach, and this cut has already removed that problem, which is why your true size is almost always the right call.
How does women's sizing differ?
The common assumption is that women's kit is just men's kit made smaller, and that is exactly what the women's range is not. It is engineered by THETA's female athletes rather than shrunk from a unisex pattern, so the fit reflects a women's shape. The Women's Race Singlet re-shapes the same record-setting race system for a women's fit, staying ultra-light with laser-cut ventilation, and the Women's Race Short is built for freedom of movement with controlled structure that stays clean in silhouette under intensity, unlike loose run shorts that lose shape. The Women's Gym Shorts use a seamless, squat-proof nylon and elastane build with a three-tier waistband for support under load. For women's pieces, then, take your normal size and trust the women's-specific cut rather than comparing to a unisex top.
How do you choose your size with confidence?
Work through it in order and you will land the right size first time.
- Decide your preferred feel: true performance fit or a slightly looser body.
- For a performance fit, take your normal size across tops, shorts and half tights.
- For a looser top, size up one and accept a slightly less fitted chest.
- Remember the fabric stays light when soaked, so tops do not need to be worn tight.
- For women's pieces, use the women's-specific cut and take your normal size.
What if you are between sizes?
Between sizes, the rule is short and splits by garment. On tops, go up if the piece is mainly for daily training and you want comfort, go down if it is mainly a race top and you want the closest fit, since the ultra-light fabric breathes either way. On shorts and half tights, always go to the size that gives a secure waistband without pinching, because a bottom that slips under load is a worse fault than one that sits a touch close. That is the whole decision; there is no need to size differently piece by piece beyond it.
The reason the smaller size so often reads true is worth naming, because it saves people a return. The tops are cut fitted across the chest, so a body that sits right on the boundary usually finds the smaller size holds cleanly rather than tightly, with the relaxed stomach giving back any room the chest takes. Order the larger size on a top and it tends to move from fitted to loose in one step, flapping where you wanted it close. If you genuinely cannot decide and the piece is a training staple you want to live in, the larger size is the safer comfort call, but for anything you will run or race in, the smaller of the two is the choice that keeps the cut doing its job.
Common questions
How does THETA sizing run in 2026?
Tops are cut fitted across the chest and relaxed on the stomach, and shorts use a close, fitness-racing-specific fit. Take your normal size for a performance fit, or size up one on tops if you prefer more room through the body.
Should I size up in THETA tops?
Take your normal size for a true performance fit, since the tops are already cut relaxed over the stomach. Size up one only if you specifically want a looser feel through the body, accepting a slightly less fitted chest.
Is the women's range sized like the men's?
No, the women's range is engineered by THETA's female athletes for a women's shape rather than shrunk down from a unisex pattern. Take your normal size and trust the women's-specific cut rather than comparing to a unisex top.
How should half tights fit?
Half tights are designed to sit close and supportive, with a sweat-wicking liner and multiple pockets, so take your normal size. The close fit is intentional and keeps the gel and phone pockets secure without bouncing.
Does the fitted cut mean I should size up?
No, the cut is fitted across the chest but already relaxed over the stomach, so your normal size gives room where you need it. Sizing up loosens the chest too, which lets the top flap on runs. Take your usual size unless you specifically want a looser body.
Sources
- HYROX official race format and station standards (hyrox.com)
- THETA product development and Elite 15 testing, 2024-2026
- Established principles of performance apparel fit and construction