It is simple to purchase men's underwear in the wrong size. Then you take your usual M or L and order it and then discover that the waistband has a snug fit or that the fabric tends to ride up.

It is not always a size label that is the issue. The S, M, L and XL sizes are not consistent sizes. Various brands offer an assortment of sizes, cuts and fabrics. Clothing sizing is defined as ISO clothing-sizing guidance, as different brands and markets may offer different sizing.

This men’s underwear size guide shows you how to measure your waist and hips, read a size chart and spot the difference between underwear that is too tight and underwear that's too loose. 

Why Underwear Size Labels Can Be Misleading

A medium from one brand might not be equivalent to a medium from another. That is normal. A brand sets its own size ranges according to the measurements and fit that it designs. The cuts are also very important. A fitted boxer brief, a loose boxer and a brief do not fit on the body in the same way.

Research specifically on men's underwear found that simple S/M/L/XL sizing can fail to reflect differences in male body shape. In a study using 3D body scanning, researchers examined 38 men aged 20–26 and identified additional lower-torso measurements that could improve underwear design and fit. 

How to Measure for Men’s Underwear

A flexible measuring tape is needed. Measurements should be taken in a natural standing position. Try to avoid drawing in your stomach and do not tighten the tape to get a smaller number. 

Measure your waist

Wrap the tape around the waistband of the underwear as it would fit generally. Level it all around your body. The tape must touch your skin or light clothing but not press in on it.

Measure in inches or centimetres as per the size chart of the brand. For example, if you measure 34 inches, do not automatically choose Medium, Large or any other size. Use that brand's chart to locate 34 inches and determine what size range it falls into.

A 2023 study collected 3D body-scan data from 378 men and analysed 48 body measurements to develop a men's clothing sizing system. The resulting 23-size system covered 99.7% of the sizing demand within the study population. 

Measure your hips

Keep feet together and stand straight. Wrap the tape around the fullest part of your hips and seat. Make sure the tape is level. Avoid letting it fall at the rear or come up at the front.

Again, please make it comfortable and not tight. Hip measurement plays an important role because the underwear must move over the hips, upper thighs and seat. This is particularly helpful when purchasing boxer briefs. 

Check your numbers

Measure twice. Check the positions of the tape and repeat if different results. Record the waist and hip sizes before referring to the brand's size chart. It takes only a couple of minutes and is more accurate than making a guess based on your old underwear.  

National Institute of Standards and Technology examines anthropometric measurements used in apparel sizing and fitting, highlighting the importance of accurate body-dimension data when developing clothing sizes.  

How to Use a Men’s Underwear Size Chart

A men's underwear size chart usually provides a size and a body size, like waist size or waist-and-hip size ranges. Always use the chart for the same brand and product that you are purchasing.

For example, imagine a brand lists: 

These are only indicative numbers. They are not a standard men's underwear size. In this example, a waist size of 35 inches fits you in size L, but another brand could be using the same size for a waist that is 32 inches.

That is why it is important to look for a universal statement like 34-inch waist equals Large, as it does not always fit properly. 

What if your waist and hips suggest different sizes?

Always consult the brand's instructions. A slight size difference might not be an issue if the underwear is very stretchy. If the smaller size puts pressure on your waist or thighs, then moving a size up will provide more comfort.

Avoid the smaller size because you believe that a tighter undersuit will provide better support. Good support comes from the garment's design and construction. Do not mistake tightness for a correct fit. 

How Should Men’s Underwear Fit?

A good piece of underwear will not restrict movement. One of the simplest to check is the fit of the waistband. It should remain on the surface and not penetrate the skin. You should not have to keep pulling it down or up during the day.

The cloth around the hips and buttocks should be pulled tight but not so tight as to cause pain. Boxer briefs should be wide enough to allow for freedom of movement without continuously pushing up against the groin.

A quick test can aid. Put the underwear on and walk around. Sit down. Bend over. Stand up again. If you suspect you can see the waistband, legs or fabric moving, listen. That movement is telling you something about the fit. 

Signs Underwear Is Too Tight

The most apparent indication is pressure. Common signs underwear is too tight include:

1. The waistband is pressed into your skin.
2. Strong pressure marks on leg openings.
3. The fabric tightens over your hips or butt.
4. Sitting and/or moving is restricted.
5. The undergarments ride up again.
6. Chafing occurs while the person is moving.
7. The front is compressed or feels uncomfortable.
8. You feel relief as soon as you take the underwear off.

Do not confuse a close fit with an overly tight fit. Fabric that is tight to the body does not cause discomfort when stretched. If you constantly notice pressure, try the next size or a different cut. 

Signs Underwear Is Too Loose

Look for these signs underwear is too loose:

1. The waistband becomes loose when walking.
2. The seat looks or feels baggy.
3. Underpants woven fabric bunches.
4. The legs lift off the ground.
5. You make constant changes to your underwear.
6. The front doesn't stay comfortably in position.
7. Excessive material around hips.

The loosest size is not the right size. Underwear should be snug enough to remain in place. 

Common Underwear Sizing Mistakes

Using your old size

Your old underwear may have stretched, shrunk or simply come from a different brand. Use your current body measurements when buying a new product.

Measuring your trousers

A label on a pair of trousers is no good as a body measurement. Take the measurement of your waist directly.

Pulling the tape tight

This can make your waist appear smaller than it is. Do not apply the tape too tightly and avoid it pulling on the skin.

Ignoring the hips

If a brand offers hip size information, then use that. They can assist in understanding why the waistband fits but the seat and/or thighs do not. 

Choosing a smaller size for support

Tight does not necessarily translate to supportive. The fit should be adjusted if the waistband is snug or causing some restriction in movement.

Ignoring the cut

Briefs, trunks and boxer briefs are all of varying shapes. Within one brand, the same size can offer a different feel depending upon style.

What to Do When You're Between Sizes

Begin with the size chart. Next, consider the location of your measurement in the range. If you are on the higher end of a size and your waistband is snug, the next size might be a better fit.  If you are closer to the bottom size and the underwear is loose, then it might be better to go with a smaller size.

When it comes to a stretchy fabric like modal, the stretch is fine, but it's not an excuse not to take measurements. If both sizes are viable, then comfort in motion is what matters. 

Quick Men’s Underwear Fit Checklist

Before choosing a size, look at these five items:

1. Waist: Waistband does not dig in.
2. Hips and seat: The cloth fits your body without sagging or bunching.
3. Legs: Does not ride up or cut into thighs.
4. Front: Support while not being too loose.
5. Movement: Walking, sitting and bending don't require constant adjustment.

Do not assume that the size is wrong if one area feels wrong. The issue may be the cut or construction. 

FAQs

How do I choose underwear size?

Take measurements of the waist and hips and then refer to the brand's size chart. Avoid using just S, M, L or XL.

How tight should men's underwear be?

It should be comfortable and feel safe. The waistband should not be tight on the skin and the material should not prevent any movement.

What if my underwear is tight? Should I make the size larger?

If this belt is not loose around the waistband, legs or seat, compare with the next size. If your measurements are already within the larger sizing, then you might want to go up a size.

Why do my underwear rise?

Riding up may be associated with size, leg opening, rise, fabric stretch or cut of the underwear. If resizing doesn't help, go with another style.

Do you want your underwear to leave marks?

It is not always a cause for concern if a child gets a light temporary impression. Discomfort or deep pressure marks, particularly if coupled with discomfort, indicate the fit may need to be adjusted. 

Final Takeaway

The best way to find a correct size for underwear is to avoid label reading. Waist measurement is taken at the waistband level. Take the circumference of the widest point of the hips. Look at those numbers and compare them to the brand's chart then see how the underwear moves when you move.

A good pair does not bunch or sag; it does not dig in. If you are looking for modal underwear, the soft, flexible fabric may make it even more comfortable, but it's still important to have the proper fit, size and cut. This combination is more important than the size label S, M, L or XL.