Men's Underwear Sizing: How to Measure and Choose

Most badly fitting underwear is bought in the right nominal size. The problem is that the size was guessed from a trouser label, and trouser labels have drifted away from actual measurements for decades.

Measure your waist properly

Stand relaxed, breathe normally, and put the tape around the narrowest part of your torso — usually just above the hip bones and below the ribs, not at the level your jeans sit.

Keep the tape level all the way round and snug without compressing. Do not pull it tight to get a smaller number; underwear that is too small rides up and rolls at the waistband, which is worse than a pair that is slightly loose.

Write the number down in centimetres and in inches. Size charts use both, and converting in your head is where mistakes happen.

Why your jeans size is not your underwear size

Two things separate them.

First, jeans usually sit on the hips, several centimetres below the natural waist. A garment measured at the hips will read larger than the same body measured at the waist.

Second, vanity sizing: many trouser makers label a waistband generously, so a pair marked 32 may measure noticeably more. Underwear brands generally publish real body measurements instead, which is why the two numbers disagree.

The practical consequence is that a man who buys 34 jeans is frequently a medium in underwear, not a large.

Reading a size chart

Charts come in two forms and it is worth checking which you are looking at.

• Body measurement charts tell you the waist the garment is designed to fit. Match your measurement to the range and you are done.
• Garment measurement charts tell you the flat dimensions of the item itself. These are smaller than your body measurement, because the fabric is meant to stretch. Do not compare them to your waist directly.

If a range straddles your number — for example a medium covering 81 to 86 cm when you measure 86 — you are at the top of that size, not the bottom of the next one.

Between two sizes: the elastane rule

This is the only decision that genuinely depends on the fabric.

With around five per cent elastane, take the smaller size. Stretch fabric conforms and needs a little tension to stay in place; sized up, it will sag and the leg will ride.

With no elastane, take the larger size. Non-stretch fabric cannot adapt, and a pair that is slightly small will simply be tight at the waistband and the thigh — and will get tighter after the first wash.

Two other measurements that matter

Inseam length controls ride-up more than waist size does. A leg ending mid-thigh has friction to hold it in place. Brands rarely put this on the front of the pack, but it is usually in the product detail.

Rise is the distance from the waistband to the crotch seam. A short rise sits below the natural waist and can pull downward when you sit; a longer rise stays where you put it. If underwear keeps sliding down, rise is the likely cause, not size.

Checking the fit at home

Try a new pair on and do three things: sit down, walk a short distance, and crouch.

• If the waistband rolls or digs in when seated, it is too small.
• If the leg creeps upward while walking, the inseam is too short or the seat is too tight.
• If there is loose fabric at the front or the waistband slides down, it is too large.

A pair that passes all three will still fit after fifty washes, provided the waistband is a covered one.