T-Shirt vs Undershirt: Top 9 Ways They Are Different

Once upon a time, the t-shirt and the undershirt were one and the same.

Over time, though, they evolved into two entirely different garments with distinct purposes.

These days, the t-shirt vs. undershirt debate often comes down to more than just semantics. It’s about functionality, comfort, and style.

In this article, we’ll explore the key differences between t-shirts and undershirts, answer common questions (like whether you can swap one for the other), and take a closer look at why choosing the right shirt matters.

Let’s dive in.

What Is The Difference Between A T-Shirt & Undershirt?

In simple terms, a t-shirt is outerwear. An undershirt is underwear.

A well designed and properly fitting undershirt should not be worn as a t-shirt. Similarly, a t-shirt can’t function as an ideal undershirt.

To provide an analogy, it would be like wearing dress shoes to run a marathon. While you can run in dress shoes, you will run much faster and more comfortably in running shoes — shoes specifically designed for the purpose of running.

It’s the same with t-shirts and undershirts. Before you invest in an undershirt, you should know what you’re signing up for.

Below are the key differences between a t-shirt and an undershirt that you need to know before you get dressed for work.

Be sure to check out the T-Shirt vs Undershirt Infographic at the end of this article!

A Brief History of T-shirts & Undershirts

To better understand the difference between t-shirts and undershirts, it helps to take a quick look at the history of the two.

T-shirts originated in the late 19th century, after the Industrial Revolution. Back in the day, workers would cut their jumpsuits in half so that they could stay cool at work during the warmer months of the year.

The first-ever manufactured t-shirt came into being around 1913 when the United States Navy began issuing t-shirts as standard undershirts.

The term “t-shirt” joined the English dictionary thanks to F. Scott Fitzgerald’s novel This Side of Paradise.

T-shirts didn’t become a wardrobe staple in their own right until 1950. Up until that point, t-shirts were worn exclusively as undershirts.

Then came Marlon Brando in A Streetcar Named Desire and James Dean in Rebel Without a Cause, both sporting t-shirts as standalone garments.

It was a striking political statement because at the time, wearing just a t-shirt was like walking out the door in just your underwear.

As t-shirts took off as everyday garments and began being printed with slogans, they cut a separate path from undershirts, which remained an undergarment a la underwear.

9 Key Differences Between T-Shirts & Undershirts

That history should help illuminate a few key differences between your average t-shirt and an undershirt.

These days, the two might look the same, but there’s actually a number of significant differences between them.

Here are nine key differences between these two garments, affecting how, when, and where you should wear them.

1. Wearability

First thing’s first: wearability.

T-shirts and undershirts may have started out as the same thing, but they’re not anymore.

Undershirts originated from the union suit, which men used to protect their skin from itchy clothing and to keep their clothes from becoming sweaty and smelly. Eventually, the union suit was split in two (thus the origin of long johns) but the appeal of the idea never went away.

Undershirts are like underpants, which are exactly what the name implies. Undershirts = under your shirt, just like underpants = under your pants.

So, much like you wouldn’t go outside with your underwear out for the world to see, you shouldn’t go outside wearing an undershirt like a t-shirt.

A t-shirt on the other hand, is meant to be appreciated in all its James Dean rebellion glory. You can wear a t-shirt just like a normal shirt.

In some very rare cases a t-shirt could double as an undershirt. But these days, it’s MUCH less comfortable to wear a t-shirt instead of an actual undershirt when the occasion demands it.

2. Thick and Thin

That’s because of a thickness difference between the two shirts.

Undershirts are made to be worn under another shirt. These days, you usually see undershirts worn under collared button-up shirts (with and without a tie).

Undershirts are much thinner and lighter than t-shirts. And because they’re meant to be worn under your actual shirt, they normally only come in white, grey, nude (tan), and black.

T-shirts are a different story. Since they’re made to be worn as a shirt on their own, they’re thicker than undershirts. They also come in all sorts of colors with a variety of designs for you to choose from.

Looking for more information about lightweight undershirts? Be sure to check out my Thin Undershirts That Keep You Cool article.

3. To Stink or Not to Stink

This brings us to our next question: to stink, or not to stink?

You see, undershirts today are primarily worn underneath a shirt. There are two reasons for this. The first is coverage. You don’t want your nipples awkwardly showing through your dress shirt, for example.

The second is the stink. Specifically, to prevent it. When you move and sweat during the day (even a little bit of sweat) an undershirt is there to keep sweat from soaking into your outer shirt.

Many undershirts are made with fabrics that have antimicrobial and anti-odor properties. Most t-shirts are not. So, if you wore a t-shirt as an undershirt, there is a distinct possibility that your t-shirt could actually stink by the end of the day.

Want to learn about wearing undershirts under dress shirts? Check out my Best Undershirts To Wear Under White Dress Shirts article.

4. Length

Another critical difference between t-shirts and undershirts is the length of the shirt.

Since an undershirt is designed to be worn underneath a shirt, it’s longer than most regular t-shirts. This is for a purely practical reason: since an undershirt is designed to go unnoticed, it has to stay tucked into your pants.

So, having a longer undershirt prevents the shirt from coming loose every time that you move.

A t-shirt, on the other hand, is more variable. As a rule, they’re not as long as undershirts since most people prefer a shorter cut for their shirts so they can be worn untucked.

Check out my Best Men’s Tall Undershirts article for a list of longer undershirts.

5. Sleeve Length

The same basic logic applies to the sleeve length.

An undershirt is intended to go unnoticed underneath your clothes. For this reason, the sleeves are generally shorter than a t-shirt – you don’t want the lines of your undershirt showing through your sleeves.

This makes it possible to wear an undershirt under a long-sleeved or short-sleeved shirt.

The sleeves on an undershirt also tend to be more fitted than a regular t-shirt. With a t-shirt, on the other hand, the rules are much looser. Sleeves tend to be longer and looser for a more comfortable fit and a more relaxed cut.

Are your undershirt sleeves too long? Check out this article for more information.

6. Find the Right Fit

And speaking of fit, the fit between a t-shirt and an undershirt is also quite different.

The entire point of an undershirt is that it’s, well, under your clothes. You don’t want to walk into work looking like you’re prepared for the Arctic (or, at least, wearing another shirt underneath your shirt).

Undershirts are much more fitted than most t-shirts so they will not add additional bulk under your shirt. Also, a fitted undershirt will help your shirts drape better.

7. Keep Cool vs. Look Cool

It might sound counterintuitive, but wearing extra clothes can actually help you cool down (at least, if one of those layers is your undershirt).

In order to maintain a consistent core body temperature, the human body sends blood to the surface of the skin and sweats. As the sweat evaporates, heat evaporates off the body and helps cool you down.

The key component here is evaporating sweat. If your sweat doesn’t have anywhere to wick off, you won’t be able to get any cooler.

This is where an undershirt can help. It helps wick moisture off your body and keep it from settling on your clothes.

This also helps you keep sweat off of your clothes, avoiding those dreaded pit stains.

Curious about what moisture wicking is? Check out my Moisture Wicking Undershirts article for loads of great information.

8. Collar Styles

The collar situation is another point of disparity.

As a rule, undershirts have a deeper v-neck than a t-shirt. There are other options available for those who don’t like such a plunging neckline under their clothes, but the v-neck isn’t for aesthetics.

Wondering where to buy deep v-neck undershirts? Check out this article covering the top deep v-neck undershirts and where to buy them.

Like most features of the undershirt, the v-neck is there because it helps the shirt go undetected under your opened collared shirts. You can get the benefit of an undershirt without anyone actually knowing you’re wearing an extra layer under there.

T-shirts vary widely depending on style and personal preference. Since it’s a shirt worn on its own, the choice is yours. You could rock a crew neck, or you could go all-in for a v-neck.

9. Underwear vs. Outerwear

Finally, in case the message hasn’t sunk in yet: the difference between an undershirt and a t-shirt is the difference between underwear and outerwear.

An undershirt is your undercover support system. It adds a layer of sophistication (and some sweat-wicking action) to keep you cool as a cucumber, even in high-pressure situations.

A t-shirt is an all-around hang out shirt. It can be dressed up or down, depending on the shirt and how you wear it, but it’s a shirt in its own right. It’s meant to be viewed and appreciated by the world (or, at least, those around you who appreciate your taste in t-shirts).

Top 7 Differences Between A T-Shirt & Undershirt

T-Shirt	Undershirt
T-shirts are generally thicker so they can be worn by themselves.	Undershirts should be thinner — to keep you cool.
T-shirts are mostly worn by themselves, without an undershirt. They come in direct contact with sweat, body oils, and odors. They should be washed after every wear.	Undershirts provide a layer of defense between your body and your shirt. They will protect your shirts from sweat, stains, & odors. Since your outer shirt will stay cleaner, you may wear it more than once before washing.
T-shirts are shorter, so they can be worn untucked, without being too long.	Undershirts are longer so they stay tucked.
T-shirt sleeves are generally longer since they are worn by themselves.	Undershirts have shorter sleeves, so they can be worn under short-sleeve shirts, such as polo shirts, as well as long sleeve shirts.
T-shirts have a shallower v-neck. While deep v-neck t-shirts do exist, they are not widely worn.	Undershirts have deeper v-necks. This keeps the collar hidden with an open collar.
T-shirts are looser fitting to accommodate different body styles, and mask any perceived imperfections (belly, love handles, puffy nipples, etc.)	Undershirts are close fitting or fitted so they don’t add extra bulk under your clothes.
T-shirts are outerwear, though can be also used for layering to achieve a particular style/look.	Undershirts are underwear. The general rule of thumb is that they should remain hidden, like underwear.

To help illustrate the difference, here is a visual guide showing the difference between t-shirts and undershirts.

To share only the infographic below, right click on the image, select Copy, then visit Facebook or Twitter, begin a post or tweet, and select Paste.

About Tug Samarreta

Tug Samarreta is the world's undershirt & underwear expert. He is also one of the most knowledgeable individuals on sweat management solutions, men's shapewear, grooming, and new fabric technologies. Got a question? Visit the contact page and send a message.