Why sizes vary between product types

Short answer: Each type of garment is designed for its own purpose, so the ease allowance differs. A close fitting base layer and a loose top in the same letter size do not share the same measurements, and that is completely normal.

Purpose decides the allowance

A base layer has to fit close to work, while a top needs room for layers underneath and for free movement. That is why bamboo undershirts for men and a top in the same letter are not alike. The letter tells you where the garment sits on the scale, not how much space there is between fabric and body.

What ease allowance means

Ease allowance is the difference between your body measurement and the garment measurement. A close fitting garment has little or no ease, because the fabric should lie against the skin. A loose garment has more, so it drapes freely and can be worn over other clothes. The maker chooses this, which is why size tables vary.

Fabric changes the need

A fabric with elastane can be smaller than the body and still feel comfortable, because it gives. A fabric without stretch must be larger than the body, or it will pull when you move. The same applies to a bamboo jogging suit with or without stretch, where the same size can feel quite different depending on the fabric.

The cut matters too

Two garments with the same chest measurement can fit differently because the cut differs. A top with a dropped shoulder seam feels wider, and a style with a narrow waist feels closer. So look beyond the chest measurement to the length and the fit description before you choose. That gives a clearer picture of how it will sit.

Use the measurements for each type

Look up the measurements for that specific type of garment rather than relying on the letter. If both body and garment measurements are listed, use both. The body measurement shows your size, and the garment measurement shows how much room there is. Check the guides on the items in the most popular styles for men.

Measure something you know

The safest comparison is a garment of the same type that you already own and like. Lay it flat and measure the width under the arms and the length. Compare with the garment measurements of the new item. If the numbers are close, it will fit the same way. That works better than borrowing a size from a different type.

Why one letter is not enough

Many people carry one size in their head and buy it across everything. That often works within the same type, but less often when moving from underwear to tops or from close fitting to loose styles. A letter is a starting point, not the answer. Treat it as a direction and let the numbers make the final choice.

A simple system for everyday use

Keep a short list of the size that fits you in each type, such as undershirts, underwear and jogging suits. Add the garment measurements of your favourites next to it. Then you do not have to start over each time you buy something new, and you avoid surprises from a garment that fits differently than expected.

Frequently asked questions

How big is the difference usually

Four to ten centimetres of allowance between close fitting and loose garments is common. That is why the same letter can feel very different between types.

Can you use the same size everywhere

Only within the same type and the same range. If you switch type, check the measurements again even if the letter stays the same.

What do you do with new types

Check the guide the first time and note the number. Next time you can use that size directly without measuring again.