UK Clothing Size Guide
, by Daniel Berry , 8 min reading time
UK Clothing Size Guide: Nike, ASICS, Under Armour, Berghaus, Trailberg & Montirex
Finding the right clothing size can sometimes be confusing, especially when shopping across different brands. A Medium in one brand may fit slightly differently to a Medium in another, depending on the cut, intended use and style of the garment.
At StrideModeUK, we stock clothing from some of the biggest names in sportswear and outdoor fashion, including Nike, ASICS, Under Armour, Berghaus, Trailberg and Montirex.
To make choosing your size easier, we have put together this UK clothing size guide, along with information on how each brand generally fits.
Quick UK Clothing Size Guide
The table below provides a useful starting point for men's clothing across many of the brands we stock.
Please note: These measurements should be used as a general guide. Individual garments can fit differently depending on their style, fabric and intended fit. Always check the specific product description where possible.
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Nike Clothing Size Guide
Nike is one of the most popular sportswear brands in the UK, and its clothing generally follows a familiar XS–XXL sizing structure.
For men's tops, Nike's official size guide uses body measurements, with a Medium generally covering a chest measurement of approximately 37.5–41 inches, while a Large covers approximately 41–44 inches. Nike also provides separate measurements for tops, bottoms, unisex clothing and other categories.
How does Nike clothing fit?
Generally: True to Size.
Most Nike T-shirts, tracksuits, hoodies and jackets will fit as expected if you choose your usual size. However, the exact fit depends on the product:
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Standard fit: A comfortable everyday fit.
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Slim fit: Closer to the body.
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Loose or oversized fit: More room and a relaxed appearance.
StrideModeUK Recommends
We recommend choosing your usual size for Nike clothing.
Nike generally fits true to size across most T-shirts, hoodies, tracksuits and jackets. If the product has a Standard Fit, your usual size should provide a comfortable everyday fit.
For Slim Fit products, consider sizing up if you prefer more room. For Loose or Oversized styles, we recommend sticking with your usual size unless you want an extra-baggy fit. Please read our product descriptions.
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ASICS Clothing Size Guide
ASICS clothing is designed primarily around running and athletic performance. The range includes T-shirts, shorts, jackets, trousers and other technical sportswear.
How does ASICS clothing fit?
Generally: True to Size, often with a performance-focused fit.
ASICS clothing can feel slightly more streamlined than casual streetwear because many products are designed for running and movement. Technical tops and jackets may sit closer to the body, while everyday training pieces can offer a more relaxed fit.
If you prefer a looser, more casual look, particularly with running tops or lightweight jackets, consider checking the product's individual fit description.
StrideModeUK Recommends
We recommend choosing your usual size for ASICS clothing.
ASICS generally fits true to size, especially for everyday T-shirts, shorts and training wear. However, some performance-focused pieces can have a slimmer athletic cut. If you prefer a more relaxed fit or are between sizes, we recommend sizing up. Please read our product descriptions.
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Under Armour Clothing Size Guide
Under Armour offers one of the most detailed approaches to fit, with products often described as Compression, Fitted, Regular, Relaxed or Oversized.
For men's tops, the official size guide places a Medium around a 38–40 inch chest, with Large around 42–44 inches. Bottoms are also sized separately using waist and hip measurements.
How does Under Armour clothing fit?
Generally: True to Size, but the fit category matters.
This is particularly important when buying Under Armour:
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Compression: Very tight, second-skin fit.
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Tight: Snug and close-fitting.
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Fitted: Streamlined and close to the body.
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Regular: Neither too tight nor too loose.
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Relaxed: More generous with additional room.
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Oversized: Deliberately loose and spacious.
StrideModeUK Recommends
We recommend checking the product description carefully, as two Under Armour garments in the same labelled size can feel very different depending on their intended fit. Please read our product descriptions.
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Berghaus Clothing Size Guide
Berghaus clothing is designed for outdoor use, including jackets, fleeces, base layers, T-shirts and technical clothing.
Its official men's sizing is based on body measurements. A Medium generally corresponds to a 39–41 inch chest, while a Large corresponds to a 42–44 inch chest.
How does Berghaus clothing fit?
Generally: True to Size, but consider layering and garment type.
A Berghaus T-shirt or fleece may fit differently to a waterproof or insulated jacket. Outdoor jackets are often designed with enough room to accommodate additional layers underneath.
When choosing a Berghaus jacket, think about how you intend to wear it:
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Everyday wear: Your usual size will normally be the best starting point.
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Layering underneath: Consider whether you regularly wear thick hoodies or fleeces beneath your jacket.
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Technical or performance use: A closer fit may be intentional.
StrideModeUK Recommends
We recommend choosing your usual size for everyday wear.
If you are buying a Berghaus jacket specifically to wear over thick hoodies or multiple layers, consider sizing up for extra room. For T-shirts, fleeces and lighter layers, we would generally recommend sticking to your normal size. Please read our product descriptions.
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Trailberg Clothing Size Guide
Trailberg creates technical sportswear and outdoor-inspired performance clothing, including T-shirts, hoods, windbreakers, shorts, trousers, tracksuits and twinsets.
The brand recommends checking the individual size guide on each product page for detailed measurements and fit information.
How does Trailberg clothing fit?
Generally: True to Size.
Trailberg garments are typically designed around movement and performance, meaning some pieces may have a more athletic or streamlined cut than traditional casual clothing.
For most customers, we recommend choosing your usual size. If you prefer a relaxed fit, or are between two sizes, sizing up may provide more room depending on the garment.
StrideModeUK Recommends
We recommend choosing your usual size for a standard athletic fit.
If you prefer your clothing to fit more loosely, particularly with technical jackets, performance tops or fitted tracksuits, consider going up one size. If you are between two sizes, we would generally recommend sizing up for a more relaxed fit. Please read our product descriptions.
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Montirex Clothing Size Guide
Montirex uses detailed chest, waist and hip measurements across its men's and women's ranges.
For men's clothing, the official guide places:
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Small: approximately 36–38 inch chest
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Medium: approximately 38–40 inch chest
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Large: approximately 40–42 inch chest
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XL: approximately 44–46 inch chest
How does Montirex clothing fit?
Generally: True to Size with a modern, athletic fit.
Many Montirex products are designed with an activewear-inspired silhouette. T-shirts, tracksuits and performance pieces often have a relatively streamlined fit without necessarily being restrictive.
If you are between sizes, we recommend considering how you prefer your clothing to fit. Choose your usual size for a more fitted or standard appearance, or size up if you prefer a looser fit.
StrideModeUK Recommends
We recommend choosing your usual size for a standard fit.
Montirex clothing generally has a modern, athletic silhouette. If you prefer a looser or more relaxed look, or if you are between sizes, we recommend going up one size. Read our product descriptions.
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Between Two Sizes?
Here's What We Recommend
If you fall between two sizes, your choice will usually depend on how you prefer your clothing to fit.
Choose the smaller size if:
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You prefer a closer or more fitted appearance.
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The garment is designed with a relaxed or oversized fit.
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You are at the lower end of the measurements for that size.
Choose the larger size if:
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You prefer a looser or more relaxed fit.
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You plan to wear layers underneath.
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You are at the upper end of the measurements for your usual size.
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The product has a slim or performance-focused cut.
We offer returns and exchanges on all items within a 14 day period! If you are unhappy with the fit and would like a different size just contact us!
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Still Unsure About Your Size?
The best reference is often clothing you already own. If you have a Nike, ASICS, Under Armour, Berghaus, Trailberg or Montirex item that fits you perfectly, use that as a starting point when choosing similar products.
Sizing can vary between brands and even between individual products, so we always recommend checking the measurements and product description before ordering.
If you are still unsure, feel free to contact StrideModeUK before placing your order and we will do our best to help you find the right size.
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