Alien T-Shirt Sizing Guide | Match Your Favorite Tee

Alien T-shirt sizing depends entirely on the retailer, so measure a tee you own and compare it to that product’s chart.

Alien-branded shirts are made by many different licensors, each using its own blanks and measurement standards. Because of this, the only reliable way to find your fit is to measure a shirt you already own and compare those numbers against the specific product’s size chart. Tag size alone won’t save you from a shirt that’s too tight or swimming on you. If you’re looking for the best licensed options to measure against, our roundup of the best Alien t-shirts worth buying covers top-rated picks across brands.

How To Measure A T-Shirt You Already Own

Lay the shirt flat on a smooth surface and smooth out any wrinkles. Grab a flexible measuring tape and take three key measurements: width, length, and sleeve length.

For the body width, measure straight across the chest from side seam to side seam, usually about 1 inch below the armpits. Double that number if you want a full chest circumference estimate. For body length, measure from the highest point of the shoulder near the collar straight down to the bottom hem. Sleeve length runs from the shoulder seam to the sleeve hem, though not every chart lists it.

Compare these numbers to the chart for the exact shirt you’re eyeing, not to a generic “Alien” size chart, because none exists across all brands.

Why Tag Size Isn’t Enough

Tag sizes are unreliable because each company picks its own blank garment. A size large from one manufacturer can match a medium from another.

The same tag size spans a huge range of actual dimensions.

Some retailers even flag the discrepancy. One Alien-branded product page tells buyers the tee is based on actual shirt measurements and that the cut runs small, recommending a size up for most people. Another notes a slim or tailored fit. If a listing mentions either, order a size larger than your usual.

Comparing Charts Across Retailers

Current listings show just how different charts can be, so check the product page before ordering anything.

Notice the pattern: some charts show flat garment width, some show body measurements like bust and waist, and some list height and weight. Mixing these up is the fastest way to order the wrong size. Flat garment measurements describe the shirt lying down, while body measurements describe the person wearing it. They are not interchangeable.

What About Costume Sizes?

Alien costume listings use a completely different system. These charts rely on height, weight, chest, waist, and inseam measurements meant for a full-body outfit, not a shirt. A costume’s size guide has zero overlap with tee sizing. If you’re buying a costume, use only that product’s own chart and ignore any T-shirt size you usually wear.

For plain tees, the fabric matters too.

When you’re ready to buy, pick a shirt from a brand with a clear chart, measure a tee at home, and compare. That method works for every Alien shirt on the market, no matter which company printed it.