Casual vs Smart-Casual vs Formal Shirts: What’s the Difference?

Before getting into fits and fabrics, it helps to understand how shirts are broadly categorised.

Casual shirts are relaxed in both fabric and construction. Think Oxford button-downs, chambray, denim, linen and short-sleeve styles. They’re often worn untucked, paired easily with jeans or chinos, and feel at home under knitwear or lightweight jackets.

Smart-casual shirts sit in the middle. They’re usually cleaner in cut, made from finer fabrics, and work equally well tucked or untucked. A brushed cotton or twill shirt with a soft collar can move comfortably between the office, dinner plans and weekends.

Formal shirts are designed for tailoring. They’re sharper, smoother, and more structured, typically made from poplin or fine twill, with crisp collars intended for ties. These are the shirts you reach for with suits, weddings and business settings.

The key difference isn’t just how they look, but how they behave with the rest of your outfit.

How Should a Men’s Shirt Fit?

Fit is where most shirt mistakes happen. Too tight and it looks restrictive. Too loose and it feels sloppy.

Regular Fit Shirts

Regular or classic fit shirts offer room through the chest and waist, making them comfortable and forgiving. They work well for broader builds, relaxed tailoring and everyday wear, especially if you prefer ease of movement.

Slim Fit Shirts

Slim fit shirts taper through the waist and chest for a cleaner silhouette. They’re best for leaner frames or anyone who prefers a sharp, close-cut look under suits or jackets.

Modern Fit Shirts

Modern fit sits neatly between the two. It offers shape without clinging, making it one of the most versatile options for both work and casual styling.

A well-fitting shirt should:

• Sit flat across the shoulders

• Button comfortably at the collar

• Allow movement without pulling at the chest

• Tuck in smoothly without excess fabric billowing

Measuring for Your Shirt Size

Getting your measurements right makes shopping far easier and helps avoid shirts that look almost right, but never quite land.

Start with your collar size, especially for formal shirts. This is the most important measurement, as getting it wrong can throw off the entire look. Shirt collars are measured in inches and usually come in half sizes. Wrap a tape measure around your neck so it sits comfortably (not tight, but without gaping), note the measurement, then add half an inch for breathing room. If you’re between sizes, always round up for comfort.

Once the collar is sorted, look at your chest and body fit, bearing in mind that this varies more between styles and brands. Formal shirts are typically sized by collar, while casual options like Oxford cotton shirts often use S, M, L sizing. In those cases, trying a few fits is the best way to find what feels right across the shoulders and chest.

Finally, check sleeve length. Cuffs should sit neatly at the wrist bone and, when worn with a jacket, peek out slightly at the cuff. It’s a small detail, but one that makes a noticeable difference to how polished the shirt looks overall.

How to Style Shirts? Tucked vs Untucked

Tuck your shirt in when:

• Wearing tailoring

• The hem is long and curved

• You want a polished, intentional look

Wear it untucked when:

• The hem is shorter and straight

• Styling casually with denim or chinos

• Layering with knitwear or jackets

A good rule: if it looks designed to be untucked, it probably is.

What to Wear Shirts With? (And Why It Works)

Tailoring: stick to poplin or twill dress shirts with clean collars.

Denim: Oxford, chambray or casual button-downs balance structure with ease.

Chinos: almost any shirt works, depending on footwear and layers.

Knitwear or jackets: button-downs and softer fabrics layer best without bulk.

To avoid looking overdressed or underdressed, match the shirt’s formality to the rest of your outfit. A crisp dress shirt with trainers feels off; a relaxed Oxford with a sharp suit does too.

Caring for Your Shirts

Wash shirts at 30-40°C with similar colour, avoiding overloading the machine to reduce creasing. A small amount of fabric softener can help keep fibres supple. Skip the tumble dryer, as prolonged heat can cause shrinkage; instead, hang shirts on a hanger to air-dry. As they dry, many creases will naturally drop out, making ironing easier. For best results, iron while the fabric is still slightly damp and pay extra attention to collars and cuffs to keep them looking sharp.

If stains appear, pre-treat high-contact areas like the collar and cuffs with a stain remover before washing, allowing it to soak in briefly for a fresher finish.