HIIT Size Guide — Complete Sizing Reference
About HIIT: HIIT is Nike's premium performance-driven clothing line designed specifically for women's high-intensity interval training and fitness. The brand combines cutting-edge technical fabrics with contemporary design aesthetics, creating sportswear that performs during demanding workouts whilst maintaining style beyond the gym. HIIT sizing follows standard UK conventions, ensuring straightforward conversions for international shoppers. The brand is engineered for active women who demand durability, functionality, and a supportive fit during rigorous training sessions. Each garment is crafted with athletic performance in mind, featuring breathable materials, strategic ventilation, and supportive construction.
How to Measure Yourself
To ensure you select the correct HIIT size, follow these measurement guidelines. Take all measurements whilst wearing fitted clothing (not overly loose or tight) and use a soft measuring tape. Measure in the evening when your body is slightly more swollen, as this reflects how your clothing will fit during and after workouts.
- Chest: Measure around the fullest part of your bust, keeping the tape snug but not tight. The tape should run straight across your back parallel to the ground.
- Waist: Measure around your natural waistline (typically the narrowest part of your torso) without pulling the tape tightly. Keep the tape measure relaxed with slight slack.
- Hips: Measure around the fullest part of your hips and bottom, approximately 20 centimetres below your waist. Again, the tape should be snug without constriction.
- Length: For tops, measure from the shoulder seam to your desired hem length. For bottoms, measure from your natural waist down the side of your leg to your ankle or preferred length.
- Record all measurements: Write down your measurements in inches or centimetres and cross-reference them with the appropriate HIIT size chart below.
- Check both systems: Compare your measurements against both the UK sizing and international conversions to ensure consistency across different size systems.
HIIT Women's Clothing Size Chart
HIIT specialises exclusively in women's sportswear. The following chart provides comprehensive sizing information for all HIIT garments, including tops, bottoms, sports bras, and layering pieces. HIIT sizing tends to follow standard UK sizing conventions, with a design philosophy that emphasises supportive, performance-focused fits suitable for high-intensity training.
| Size Label | UK | US | EU | Bust (inches) | Waist (inches) | Hips (inches) |
|---|---|---|---|---|---|---|
| XS | 6–8 | 2–4 | 34–36 | 31–33 | 24–26 | 33–35 |
| S | 8–10 | 4–6 | 36–38 | 33–35 | 26–28 | 35–37 |
| M | 10–12 | 6–8 | 38–40 | 35–37 | 28–30 | 37–39 |
| L | 12–14 | 8–10 | 40–42 | 37–39 | 30–32 | 39–41 |
| XL | 14–16 | 10–12 | 42–44 | 39–41 | 32–34 | 41–43 |
HIIT Sportswear Fit Guide
Understanding the intended fit of HIIT garments will help you select the correct size for your training needs:
Sports Bras
HIIT sports bras are designed with high-impact support for intense training. They should fit snugly across the back and under the bust without gaping or overflow. The band should sit level both front and back. Expect a supportive, close-to-body fit rather than an oversized silhouette.
Training Leggings
HIIT leggings offer a supportive, body-conscious fit that moves with you during dynamic workouts. High-waisted designs provide core support. The inseam should reach your ankle bone without excess fabric bunching. Opt for your standard size for a performance fit that's neither too tight nor too loose.
Training Tops & T-Shirts
HIIT tops generally follow a fitted silhouette with sufficient room for breathability and movement. The hem should sit at your natural hip line or slightly below. Sleeves should end mid-bicep without binding. Consider product reviews for items that run tight or generous.
Shorts & Hot Pants
Training shorts sit at the hip with a snug waistband to prevent shifting during dynamic movement. Inseams vary from ultra-short to mid-thigh depending on style. The fit should be close to the body without restricting leg movement or creating uncomfortable bunching.
Layering & Hoodies
HIIT layering pieces offer a more relaxed, oversized fit suitable for warm-up and cool-down phases. Hoodies should allow comfortable layering over sports bras and tops. Drawstring waists provide adjustable fit. Consider sizing down if you prefer a more fitted silhouette.
Outerwear
Training jackets provide comfortable room over layered clothing whilst maintaining a streamlined silhouette. Armholes should sit at your natural shoulder point. Hem length typically reaches your hip. Check product-specific guidance for performance features like weather resistance and ventilation.
Sizing Information & Recommendations
HIIT follows standard UK sizing conventions, making size conversions straightforward for international shoppers. However, individual pieces may fit differently depending on the specific design, fabric composition, and intended purpose.
- Always check product-specific size charts: HIIT provides detailed measurements for individual items, which may vary from standard sizing depending on the garment type and fit style.
- Read customer reviews for fit feedback: Real customer experiences provide valuable insights into whether items run true to size, small, or large. Pay particular attention to comments about fit during movement and after washing.
- Consider the item type: Sports bras, high-impact leggings, and form-fitting tops will have different fit philosophies than oversized hoodies or layering pieces.
- Factor in layering needs: If you intend to wear HIIT pieces over other clothing, you may wish to size up slightly for comfort, particularly with sports bras and tight-fitting tops.
- Check material composition: HIIT fabrics may stretch or shrink differently. Technical nylon-spandex blends typically offer excellent stretch recovery, whilst cotton-blend pieces may require slightly more generous sizing.
- Contact HIIT customer service: If you're between sizes or uncertain, HIIT's customer service team can provide personalised sizing recommendations based on your measurements and fit preferences.
International Size Conversions
HIIT products are primarily sold using UK sizing, but the chart below provides quick international conversions for customers shopping from other regions:
| UK Size | US Size | EU Size | Australia/NZ | Japan Size |
|---|---|---|---|---|
| 6 | 2 | 34 | 6 | 7 |
| 8 | 4 | 36 | 8 | 9 |
| 10 | 6 | 38 | 10 | 11 |
| 12 | 8 | 40 | 12 | 13 |
| 14 | 10 | 42 | 14 | 15 |
| 16 | 12 | 44 | 16 | 17 |
HIIT Sportswear — Product-Specific Guidance
High-Intensity Training Leggings
HIIT's core offering, training leggings are engineered for maximum performance during HIIT workouts, CrossFit, running, and gym sessions. High-waisted designs provide core support and security. When selecting legging sizes, measure your inseam carefully. HIIT typically offers standard length and petite options. The fit should be close enough to prevent chafing during rapid leg movements, but not so tight that circulation is restricted. Most wearers find their standard UK size appropriate for leggings; however, if you're between sizes, sizing up is usually recommended for comfort during sweat-intensive sessions.
Sports Bras & Bra Tops
Proper sports bra sizing is critical for comfort and support during high-intensity exercise. Unlike standard bras, HIIT sports bras should fit significantly more snugly. Measure your bust at its fullest point and refer to HIIT's specific bra size chart, as cup and band sizes may differ from everyday bra measurements. The band should sit level, not riding up at the back. Underwire and encapsulation styles provide maximum support, whilst bra-top hybrids offer a seamless aesthetic. Many customers prefer to size down by one size in sports bras for maximum support during dynamic movements.
Training Shorts & Hot Pants
HIIT offers shorts ranging from ultra-short (2-3 inch inseams) to longer styles (8+ inches). Sizing for shorts should follow standard HIIT sizing guidance, though the fit varies considerably by style. Always check product photos and customer reviews to understand how each design fits. High-waisted shorts should sit at your natural waist without slipping. Pockets and phone storage vary by style. If between sizes, standard guidance is to choose your true size unless reviews indicate a particular style runs tight or loose.
Training Tops & Jackets
HIIT offers fitted training tops, crop tops, and layering jackets. Fitted tops should allow full range of motion without excess fabric. Oversized hoodies and jackets run generously and are designed for layering, so sizing up is common if you prefer additional comfort. Performance outerwear features moisture-wicking fabrics and ventilation panels. Check individual product descriptions for specific technologies like reflective elements, water resistance, and temperature ratings.
HIIT Sizing Tips — Expert Recommendations
- Measure in the evening: Your body is typically slightly more swollen after the day's activities, which more accurately reflects how HIIT sportswear will fit during and immediately after workouts.
- Prioritise comfort for high-impact activities: HIIT garments are designed for intense, dynamic movement. Never select a size so tight that it restricts breathing, movement, or circulation. Seams should sit smoothly without digging in.
- Consider moisture-wicking fit: HIIT's technical fabrics are engineered to manage sweat. A slightly snugger fit (within your true size range) allows moisture management fibres to function optimally without pooling or bunching.
- Account for material stretch: Most HIIT garments feature 4-way stretch or high-elastane content. If you prefer a more relaxed fit, you may size up; however, standard sizing typically accommodates the material's stretch properties.
- Review size-specific comments: When reading customer reviews, filter feedback by the specific size purchased. A comment from someone in a size L may differ significantly from feedback in a size S, as proportions and expectations vary.
- Use the returns policy: HIIT typically offers free returns on unworn items. Take advantage of this to order multiple sizes and determine your perfect fit without financial risk.
- Check fit adjusters: Many HIIT pieces feature adjustable elements like drawstring waists, adjustable shoulder straps, or drawcord hems. Utilise these features to customise fit after purchase.
- Allow for a wash-and-dry cycle: Before returning unworn items, ask whether specific fabrics require particular care. Some technical fabrics shrink slightly if tumble-dried; air drying preserves original sizing.
Size Chart Accuracy & Disclaimer
This size guide has been compiled from official HIIT sizing information and industry-standard conversion metrics. However, individual garments may fit differently due to variations in design, fabric composition, and manufacturing batches. Always cross-reference this guide with the product-specific size chart available on the item's product page before purchasing.
It is essential to measure your body accurately using a soft measuring tape and to compare your measurements against both the HIIT size chart and individual product dimensions. Sizing can vary between different garment types and collections. When in doubt, contacting HIIT customer service directly is advisable for personalised sizing recommendations tailored to your specific measurements and fit preferences.