FORM Activewear Sizing Guide: Leggings & Tanks That Fit Right

You've found the perfect modest activewear. The design speaks to you. The coverage is exactly what you need. Then sizing day comes, and you're staring at a size chart wondering whether to go true-to-size or take a chance. If you're eyeing FITH's FORM collection, here's the truth: most people size up, and there's a real reason why.

TikTok communities built around modest activewear have tested this extensively. The consensus is clear. And once you understand the logic behind it, picking your size becomes simple.

Related: Modest Activewear Market 2026: Is Form Worth It? Data-Driven Buyer's Guide

Related: How to Choose the Right Activewear for Gym Training

Why You Should Size Up for FORM Leggings

FORM leggings are engineered with a body-hugging design. That's the point. They're meant to support your movement, contour your shape, and deliver compression without feeling restrictive. When you order your true size, that compression can feel tighter than you'd want for a full workout session or all-day wear.

Sizing up one to two sizes solves this instantly. You get the same compression benefits and supportive fit, but with room to breathe. Your leggings stay in place during your workout without pinching at the waist or thighs. And honestly, that comfort difference transforms how often you actually reach for them.

The TikTok community doesn't recommend sizing up arbitrarily. People who've ordered multiple sizes report consistent results: one size up gives you a firmer, more compressed feel, while two sizes up delivers a looser, more relaxed fit that some prefer for longer sessions.

FORM Tank Tops: The Same Approach Works

Tank tops follow the same logic as the leggings. FORM's modest tank designs are cut to hug your frame while maintaining full coverage. A true-to-size fit can feel snug in the chest and shoulders, especially if you're layering or planning extended wear.

Size up one size for a balanced fit that moves with you without excess fabric. Size up two if you prefer a roomier silhouette or plan to layer underneath. Since modest activewear often involves strategic layering, having a bit of extra room in your tank makes that easier and more comfortable.

The beauty of FITH's sizing approach is flexibility. You're not locked into one formula. You're choosing based on your body and your preference.

How to Decide: Compression vs. Room

The sizing decision really comes down to one question: do you want compression or roominess?

If you love compression and support, choose one size up from your typical size. This delivers a snug, body-hugging fit without the squeeze. Athletes who do high-impact activities often prefer this. You get muscle support and a sleek silhouette without overheating.

If you prefer a looser, more relaxed fit, go two sizes up. This is ideal for yoga, Pilates, or low-impact workouts where mobility and freedom of movement matter more than compression. It's also the move if you run hot or plan to wear your pieces multiple times throughout the week without washing.

Caught between sizes? That's actually the easiest decision. Pick based on your compression preference. Don't overthink it.

What TikTok Users Are Actually Saying

The sizing-up trend didn't start with marketing. It started with real people trying on FORM pieces and sharing what worked. Multiple TikTok users across different body types and fitness goals report the same experience: sizing up delivers the comfort and fit they were hoping for.

That social proof matters because it's not theoretical. These are people with bodies like yours, doing workouts like yours, wanting the same modest coverage and quality fit. They've already done the testing.

One consistent theme: people regret not sizing up on their first order. But they don't regret it on subsequent orders because now they know the system.

Why Modest Activewear Fit Matters More

When you're shopping for modest activewear, fit isn't just about aesthetics. Fit affects function. A too-tight modest piece might gap or shift during movement, defeating the purpose of the coverage you chose it for in the first place. A well-fitted piece moves with your body, stays in place, and lets you focus on your workout instead of adjusting your clothes.

According to research on activewear fit and athletic performance, proper garment fit increases comfort and reduces distraction during physical activity. That's not trivial. It's the difference between enjoying your workout and enduring it.

Related: Top 7 Activewear Mistakes That Ruin Your Workout Performance

FORM's body-hugging design philosophy is built on this principle. The leggings and tanks are supposed to support your movement. Sizing correctly is how you unlock that benefit.

The FITH Guarantee Behind Your Purchase

Here's the thing about trying a new sizing approach: you're protected. FITH backs every purchase with a 30-day money-back guarantee. If you size up and it's not what you expected, you can return it. Free U.S. shipping on orders over $100 also means the cost to test your sizing preference is minimal.

That safety net is worth something psychologically. You're not gambling on fit. You're testing with confidence.

Quick Sizing Cheat Sheet

• Prefer compression and support: Size up 1 size from your true size
• Prefer relaxed, roomy fit: Size up 2 sizes from your true size
• Between sizes: Choose based on compression preference, not the size number
• Layering planned: Size up 1 to 2 sizes (depends on layer thickness)
• All-day wear planned: Size up 1 to 2 sizes for sustained comfort

This is the framework TikTok communities have tested and validated. It works across body types and fitness levels because it's based on understanding how FORM's design actually functions.

Make Your Move with Confidence

You know what you want from your activewear: modest coverage that doesn't compromise on fit, support, or style. You know what FORM leggings and tanks deliver. The only thing left is getting your size right so you can actually enjoy wearing them. Size up one or two sizes based on your preference for compression or room, and you'll see why the TikTok consensus exists. Your comfort depends on it.

Do I need to size up if I usually wear a specific size?

Yes. FORM's body-hugging design is engineered for sizing up. Your true size in FORM will feel noticeably tighter than your true size in other brands. Sizing up one to two sizes is the standard recommendation across the community, and it's not a manufacturing quirk—it's by design.

What's the difference between sizing up 1 vs. 2 sizes?

One size up gives you compression with comfort. Two sizes up gives you a looser, more relaxed fit. Choose one size up if you want muscle support and a hugged silhouette. Choose two sizes up if you prefer room to move and plan to layer underneath.

Can I return FORM pieces if the sizing doesn't work?

Yes. FITH offers a 30-day money-back guarantee on all purchases. If you're not satisfied with the fit, you can return it within 30 days for a full refund. This takes the risk out of trying a new sizing approach.

Is the sizing guide the same for leggings and tanks?

The logic is the same—size up for comfort and proper fit—but your personal preference might differ between pieces. Some people like compression in leggings but prefer roominess in tanks for layering. Test both, use the 30-day guarantee if needed, and you'll quickly figure out your preference for each piece type.