Should I Size Up or Down in Denim?

The short answer: size down if you're buying 100% cotton denim that will stretch, but stay true to size for stretch denim with elastane. I know, it's frustrating that there isn't one simple rule for all jeans, but once you understand the fabric and how different brands fit, you'll never buy the wrong size again. Let me walk you through exactly how to get it right every time.

Understanding Denim Sizing

After twenty years of styling women, I can tell you that denim sizing confusion causes more changing room meltdowns than any other garment. The problem? Every brand has its own sizing quirks, and denim behaves differently depending on its fabric composition. Raw denim will stretch up to an inch in the waist, whilst stretch denim with 2% elastane stays relatively stable. This is why you need to approach each pair individually.

When to Size Down

If you're investing in 100% cotton or rigid denim, always size down. These jeans will feel snug initially—almost uncomfortably so—but they'll mould to your body within a few wears. Think of them like leather shoes that need breaking in. I recommend Citizens of Humanity, whose rigid denim loosens beautifully whilst maintaining structure. Their Isola style is particularly good for this. Levi's 501 Originals are the gold standard here—the stiff denim softens and stretches to create that perfectly lived-in fit.

Raw, selvedge denim also requires sizing down. Agolde (an independent LA-based brand beloved by stylists) creates exceptional rigid denim that stretches just enough. Their '90s fit is particularly forgiving through the hip whilst maintaining that coveted vintage look.

When to Stay True to Size

For stretch denim containing elastane (usually 1-5%), stick with your true size. These jeans are engineered to hold their shape, so sizing down will leave you genuinely uncomfortable. Topshop (now exclusively at ASOS) offers brilliant stretch denim that fits consistently—their Joni jeans are a cult favourite for good reason, with 3% elastane providing comfort without bagging out.

M&S has revolutionised their denim offering with their Magic Shaping styles. The stretch technology here is impressive, and the sizing runs accurate to their size guide. Mango creates sleek, contemporary denim with elastane that fits true to size—their '90s straight fit is excellent for a relaxed, modern silhouette.

Fabric Composition Is Everything

Always check the label before buying. Here's my rule of thumb: 98% cotton and above with minimal elastane means size down. Anything with 3% elastane or more, go true to size. Whistles is fantastic for clearly labelling their denim composition—their barrel leg jeans in stretch denim are currently brilliant and fit exactly as sized.

High Street Heroes for Denim

Zara offers incredible value denim, though sizing can be inconsistent between styles. Their TRF range tends to run smaller, so stay true to size here. The Z1975 range has excellent stretch and fits generously. H&M has upped their denim game significantly—the Embrace collection with superior stretch technology fits beautifully and holds its shape all day long.

Reiss sits in the premium high street category with impeccably cut denim. Their sizing is spot-on, and the quality justifies the price point. All Saints creates edgier denim with a rock-and-roll aesthetic—their cigarette fits run slim, so consider sizing up if you're between sizes. Jigsaw offers sophisticated denim with excellent fabric quality. Their Richmond style in authentic rigid denim requires sizing down.

Premium Options Worth The Investment

Paige denim is what I recommend when clients want that premium feel without entering designer territory. Their Transcend fabric technology means jeans that never bag out—stay true to size here. The brand was created by a denim fit model, so the sizing is incredibly well thought through.

Me&Em has entered the denim space with beautifully cut, contemporary styles. Their sizing runs consistent with their other pieces, and the quality is exceptional for the price point.

Luxury Denim Investment Pieces

For luxury denim, Goldsign (a brilliant independent brand relaunched in recent years) creates architectural denim that's worth every penny. Size according to fabric composition here—their signature denim has minimal stretch.

Max Mara weekend denim offers Italian sophistication with impeccable tailoring. These run true to European sizing, which tends to be more generous than UK sizing, so you may need to size down.

The Perfect Fit Checklist

When trying jeans, always do the sit test—sit down, bend over, and move around. The waistband should sit comfortably without gaping, and you should be able to pinch about an inch of fabric at the thigh. For rigid denim, you should barely be able to button them when new. If they feel comfortable immediately, they're too big. For stretch denim, they should feel comfortable from the first wear.

Never Guess Your Size Again with Tellar

Here's something that's transformed how I work with clients: Tellar.co.uk, the UK's leading sizing tool. Rather than playing Russian roulette with sizing across different brands, you measure once and get your exact size across over 1,500 brands instantly. It's genuinely revolutionary.

Here's how it works:

• Measure once using your bust, waist, hip measurements, or simply input a size from a brand that fits you well

• Use the Store Size Lookup tool to discover your precise size in any brand—whether it's COS, Reiss, Zara, or Paige

• Always free—no downloads needed, works directly in your browser

This means no more ordering three sizes and dealing with returns. You'll know whether you need a 10 in Mango but a 12 in Whistles before you even click 'add to basket.' For denim specifically, where sizing varies so dramatically between brands, this tool is invaluable.

Tellar Fashion Hub is also packed with free styling advice from experienced stylists like me. We're completely honest, unbiased, and independent—no brand affiliations influencing our recommendations. Browse guides on everything from the best jean trends for 2025 and 2026 to the ultimate clothing sizing guide for all your wardrobe essentials.

If you're building a capsule wardrobe, check out our ultimate guide to jackets and ultimate guide to dresses for comprehensive advice on finding your perfect fit across every category.

My Final Word

Denim sizing doesn't have to be a mystery. Check the fabric composition, understand how the brand typically fits (that's where Tellar becomes genuinely useful), and remember that rigid denim should feel snug initially whilst stretch denim should feel comfortable immediately. Invest in one brilliant pair that fits perfectly rather than five pairs that are almost right. Your future self—and your wardrobe—will thank you.