The Fit Key

What is the Fit Key?

The Fit Key is a 5-character code printed inside every LE CHEMISEUR® shirt, on the back yoke, next to your name. It stores every measurement of your shirt — collar, shoulders, chest, waist, hips, sleeve length and back length, among others. With this Key, you reorder the exact same fit in one click, or adjust it to the centimetre, without ever taking measurements again.

The concept, patented by Jan Schütte, engineer and founder of LE CHEMISEUR®, was filed with the INPI in 2012, two years before the brand launched (patent FR3000262). To our knowledge, no other brand in the world stores the fit of each shirt this way.

How it works

1 · Your first shirt is calculated by AI

You enter your weight, height and age, then answer three questions: your build (a bit of a belly, average or athletic), how you wear your shirts (tucked in, untucked, or both — for the length) and which wrist you wear your watch on. Our AI, trained on data from more than 50,000 customers, works out your fit in a few seconds. No tape measure.

2 · Your Fit Key arrives with the shirt

It is printed on the back yoke and saved in your customer account.

3 · You reorder in one click

In your account, "Start from this shirt": another fabric, another collar, exactly the same fit. You can also adjust it: +1 cm at the chest, −1 cm on the sleeves, a little straighter for a shirt worn untucked. Every adjustment creates a new Fit Key, printed in the next shirt.

The perfect fit takes two shirts

A made-to-measure fit doesn't land by magic: it converges, and quickly. According to the Observatoire de la chemise, LE CHEMISEUR®'s shirt report, 57.6% of customers adjust at least one measurement after their first shirt (10,512 customers who ordered at least twice, 2020-2026). The most adjusted measurement is the waist, ahead of back length and chest — fine adjustments of 2 to 3 cm at the median. Then nothing moves: the final fit is reached with the second shirt (median).

That is exactly what the Fit Key locks in: your finished fit, the one that suits you, ready to be reproduced identically for every shirt that follows.

Why store the shirt, not your body measurements

A tailor measures your body, then adds ease according to his school and his taste. Two tailors, two different shirts. The Fit Key stores the measurements of the shirt itself — the garment you have worn, washed and approved. It is more reliable, and easier to adjust: you start from a shirt you hold in your hands, not from an abstract number.

Shrinkage is already accounted for. Even a premium fabric shrinks slightly in the first washes; during production, our AI adds between 1% and 3% to the measurements depending on the fabric, so that your shirt reaches exactly the measurements of its Key after two or three washes.

What the Fit Key changes

Our return rate is 5%, where online fashion runs at 20 to 30%. If your first shirt doesn't fit perfectly, the 100-day Fit Guarantee applies: our team in Paris corrects the fit, usually without you having to send the shirt back, and updates your Key for the orders that follow. And because every shirt is made to order, to your Key, we hold no stock and have no unsold goods — one of the foundations of our B Corp certification.

Adjusting your Fit Key

A few kilos more or less, a preference that changes, a more relaxed shirt for the weekend: start from your best-fitting shirt and change only what needs changing. Illustrated guides walk you through it measurement by measurement, and our experts are available free of charge, on a 30-minute video call or at the showroom in Paris. One tip: always adjust from a shirt that has been washed two or three times.