Getting the size right: measure a garment, not your chest

10/22/26 October, 26

Homme de dos en t-shirt Need Money For Porsche dans un garage, une 911 GT3 RS à contre-jour derrière lui

Size guide · Read 5 min

It is the first cause of returns on a clothing site, and it is avoidable. An M is not the same width from one brand to the next, and nobody knows their chest measurement to the centimetre. The reliable method lies elsewhere: take a garment you already like wearing, lay it flat, measure it. One minute, and the right size first time.

The one minute method

Take out of your wardrobe the t-shirt whose cut suits you. Lay it flat, without stretching it, sleeves open. Measure two things:

The width, from one underarm seam to the other, in a straight line. That is the measurement that decides everything.

The length, from the top of the shoulder to the bottom of the garment.

Carry those two numbers into our charts and take the closest size. You are no longer comparing a body to a letter, you are comparing a garment to a garment, and that is why it works.

The classic trap
Measuring your chest with a tape gives a circumference, not a flat width. The two do not compare: a garment laid flat measures roughly half the circumference, plus the ease of the cut.

T-shirts, from XS to 3XL

Seven sizes, garment measurements taken flat, in centimetres. The third figure is the wearer's height the cut is built for.

XS: 42 wide, 68 long, for 165 to 170 cm.
S: 45 and 71, for 170 to 175 cm.
M: 48 and 74, for 175 to 180 cm.
L: 50 and 76, for 180 to 185 cm.
XL: 52 and 78, for 185 to 190 cm.
2XL: 55 and 80, for 190 to 195 cm.
3XL: 58 and 82, for 195 to 200 cm.

From one size to the next, the width gains two to three centimetres. That is little: if your measurement falls between two sizes, the real difference is a finger of fabric. The full chart is on the t-shirt size guide page.

White Need Money For Porsche t-shirt worn, front view — The cut is the same across the whole t-shirt catalogue: only the print changes.

A sweatshirt is not a thicker t-shirt

This is the most common mistake, and it is measurable. At the same size, a sweatshirt is wider and shorter than a t-shirt.

In M: the t-shirt is 48 wide and 74 long, the sweatshirt is 52 and 70. Four centimetres more at the shoulders, four less at the hem. The silhouette is not the same, and that is deliberate: a sweatshirt is worn squarer, often over something else.

XS 48 and 66, S 50 and 68, M 52 and 70, L 54 and 72, XL 56 and 74, 2XL 58 and 78, 3XL 60 and 82. The wearer height references are the same as for the t-shirt. Full detail on the hoodie size guide page.

The practical consequence: if you wear M in a t-shirt and want a fitted sweatshirt, stay in M. If you really want it loose, L gives you two centimetres more, not an oversized cut.

White Tourismo hooded sweatshirt worn, straight cut — Four centimetres more in width, four less in length: the square cut of a sweatshirt.

Kids' sizes start from age, then get checked

Five sizes, from 8 to 16 years. The measurements are the garment's: length from collar to hem, chest circumference of the garment, shoulders from seam to seam, sleeve from shoulder to wrist.

XS / 8 years: 47 long, 70 chest, 32 shoulders, 15 sleeve.
S / 10 years: 51, 76, 35 and 16.
M / 12 years: 56, 83, 39 and 17.
L / 14 years: 61, 91, 43 and 18.
XL / 16 years: 66, 100, 48 and 19.

Age is only a starting point: between eight and sixteen, two children of the same age can be ten centimetres apart. If it is a gift and you hesitate, take the size up, it will be worn longer. The chart is on the kids' size guide page.

7Adult sizes, XS to 3XL

4Centimetres between t-shirt and sweatshirt in M

5Kids' sizes, 8 to 16 years

Caught between two sizes

If you like the fabric close to the body, take the smaller one. Printed cotton does not stretch in width, so what you measure is what you keep.

If you layer, take the larger one, especially in a sweatshirt: four centimetres of width are enough to fit another layer underneath.

If it is a gift, trust the person's height rather than their build: the reference column in the charts exists for that, and it is wrong less often than the eye. The whole catalogue follows the same measurements, from the t-shirts to the sweatshirts of the Formula 1 range.

Where to start

Three pieces where the size question comes up most often.

Back of a white The Porsche GT3 RS 911 t-shirt

The Porsche GT3 RS 911 T-shirtSeven sizes, two colours

Back of a white F1 Lewis Hamilton sweatshirt

Lewis Hamilton F1 SweatshirtSquare cut, seven sizes

White kids' Porsche 911 GT3 RS t-shirt, front view

Kids' GT3 RS T-shirtFrom 8 to 16 years

Seven sizesFormula 1 t-shirtsThe same cut across the catalogue. The seasonFormula 1 sweatshirtsWider, shorter, warmer. 8 to 16 yearsKids' clothingThe same worlds, smaller. No riskGift ideasWhat you can give without knowing a size.

Frequently asked questions

How do I measure without a tailor's tape?

A DIY tape measure does the job: the garment is laid flat, so you measure in a straight line, not around the body. A ruler and a mark on the floor work too.

How wide is an M?

48 cm in a t-shirt and 52 cm in a sweatshirt, measured flat from one underarm to the other. The length is 74 cm in a t-shirt and 70 cm in a sweatshirt.

Should I take the same size in t-shirt and sweatshirt?

Yes in most cases. The sweatshirt is already four centimetres wider at the same size, so going up gives a very loose cut rather than a normal one.

Does the garment shrink in the wash?

Printed cotton does not stretch in width. Wash inside out and at a low temperature to protect the print, that is the precaution that matters most.

Which kids' size for a gift?

Start from the age, then take the size up if you hesitate: it will be worn a season longer. XS matches 8 years, XL matches 16.

The letter changes from one brand to the next, the centimetres do not. Measure the garment you like once, write down the two numbers, and the question never comes back. The width, the length, the cut.

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