A letter on a label is not a measurement. It is one brand's opinion about one body, and it changes every time you change brands. Here is how to know your shirt size for certain, with a tape or without one, and how to judge a fit once the thing is on your back.
Why an L in one brand is not an L in another
Most men never learn their shirt size as a number. They learn one letter, in one brand, and hope it travels. It does not, and the reason is structural rather than careless. Nobody governs letter sizes: there is no standards body that defines a medium, and no legal chest measurement attached to XL. Each maker picks a base size, decides how much room to build into it, then steps up and down from there in fixed increments. That stepping is called grading. Change any one of those three decisions and the same letter comes out of the factory as a different garment.
Four things move the real numbers behind the letter.
- The grading rule. Most makers step 2cm of chest width and 2cm of body length between one size and the next. Others step 3cm across the chest and barely touch the length, which is why some brands feel wide and short on you at every size while others feel narrow and long.
- The body the pattern was cut for. A pattern drafted for a northern European frame starts from longer arms and a longer torso than one drafted for Egypt. Same letter on the label, different starting body underneath it.
- Vanity sizing. If a brand's shopper wants to be a medium, the brand quietly makes its medium bigger. It costs nothing to do and it sells more shirts. Over a decade the whole ladder drifts upward, and the drift is never announced.
- Flat measure against body measure. This is the one that costs people money. A chart that says "chest 100cm" might mean the chest of the man or the chest of the shirt laid flat, and those two numbers describe wildly different garments. Most charts never say which they mean.
That last point is worth pausing on, because it is the single biggest source of men's size chart differences between brands. If you read a body-measure chart as a flat-measure chart, you will order a garment roughly 10cm too small around the chest and blame the brand. Everything in the Rflx size guide is a garment measurement taken flat, in centimetres, and it says so above the tables. Before you compare any two brands, check which of the two kinds of number you are looking at.
Measure a shirt you already own, not yourself
The most reliable way to buy the right size online is to stop measuring your body and start measuring your wardrobe. Pick the top you reach for most often, the one that fits the way you want things to fit. That garment is already the answer. All you have to do is read it.
- Lay it flat on a hard surface, front facing up, buttons done.
- Smooth the wrinkles out with your palm. Do not stretch it, and do not tug the sides straight.
- Measure in a straight line from one underarm seam across to the other. That is the width.
- Measure from the highest point of the shoulder, the spot right next to the collar, straight down to the bottom hem. That is the length.
- Write both numbers on your phone. You will use them for years.
The width figure is half the circumference, so double it to get the chest of the garment. A 56cm width is a 112cm garment chest. Your own chest will measure less than that, and the gap between the two is the room you are walking around in. Once you know the width you like, comparing it to the width column, colour by colour takes about five seconds.
Why does this beat a tape around your ribs? Because a tape gives you one number and no opinion. It cannot tell you whether you like a close line or a relaxed one, and it varies every time you take it: a breath in, a slipped hand, the tape riding over the shoulder blades instead of under them. A shirt you already like has every one of your preferences baked into it. You are not estimating your body. You are copying a result you have already approved.
How to know your shirt size without a measuring tape
Almost nobody owns a tailor's tape. Almost everybody owns these, and each of them is accurate enough to choose between sizes that sit 2cm apart.
- A sheet of A4 paper. The best ruler in any flat. Its short edge is 21cm and its long edge is 29.7cm, anywhere in the world, on every sheet in the ream. Lay the sheet across the shirt, press your thumbnail where it ends, slide it along and count. Two short edges is 42cm, one long edge plus one short edge is 50.7cm, and two long edges is 59.4cm. That covers the whole range you need.
- A bank card or your national ID card. Cards are made to one international standard: 8.56cm long and 5.4cm tall. Eight card lengths across is 68.5cm. Nothing else in your wallet is that precise.
- Your phone charging cable. Flexible, which is useful, but unmarked. Calibrate it once: lay it along the short edge of the A4 sheet and put a small piece of tape at 21cm. Now you have a soft tape with one known unit, and it lives in your bag.
- A banknote. Same trick. Measure the note once against the A4 sheet, write the number in the corner of that sheet, and from then on the note is a repeatable unit you can lay end over end across a garment.
- Floor tiles. Tiles in one room are cut to one size. Measure a single tile with the A4 sheet, then lay the shirt along a grout line and count tiles and part-tiles. You have effectively turned your floor into a ruler the length of the flat.
Round to the nearest half-centimetre and stop there. You are not tailoring a suit, you are deciding between an L and an XL, and those two are further apart than any error this method will introduce.
Fit, part by part, with a test for each
A shirt does not fit or fail as a whole. It fits in six separate places, and each one fails in its own way. Check them in this order, because the first one on the list outranks all the others.
How should a shirt fit on the shoulders
Run a finger from the base of your neck outwards along the top of your shoulder until it drops over the edge and starts down your arm. That corner is where the shoulder seam belongs. Stand square to a mirror with your arms down and look at both seams.
Pass: the seam sits on the corner, and the sleeve hangs straight down from it. Fail, too big: the seam has slid onto your upper arm, the sleeve head collapses, and the whole shirt reads borrowed no matter how good the chest is. Fail, too small: the seam has crept inward towards your neck, and you can see faint diagonal lines running from the armpit up towards the shoulder.
Get this one right above everything else, because it is the one thing that cannot be altered. A tailor can take in a side seam in ten minutes for very little money. Moving a shoulder means detaching both sleeves, recutting the yoke and setting the sleeves back in by hand, which costs more than most shirts are worth. On a knit it is not really attempted at all. Buy the shoulder and adjust around it.
How should a shirt fit around the chest
Arms down, relaxed. Reach across with your opposite hand and pinch the fabric at the side of your chest, just below the armhole. You want to gather roughly 3cm to 5cm of loose cloth between your fingers.
Pass: a comfortable pinch, and the fabric releases back flat when you let go. Fail, too small: nothing to pinch, and horizontal pull lines fan out from the buttons on the placket. Fail, too big: more than 8cm gathers in your hand, and the fabric stands away from your ribs instead of following them down.
Body width and drape
Drape is what the cloth does when nothing is pulling on it. Below the chest, the fabric should fall more or less straight rather than gripping your waist or ballooning away from it. Weight matters here as much as width: a dense knit hangs and holds a line, a thin jersey clings to whatever is underneath it and shows every ridge.
The test: stand side-on to a mirror with your arms down, then raise both arms overhead and drop them. A shirt of the right width settles back into place on its own. If the hem rides up and stays up around your middle, the body is too narrow. If the sides swing and keep swinging after you have stopped moving, it is too wide.
Sleeve length on a short sleeve
A short sleeve should end somewhere between the middle of your bicep and just above the elbow. Anything past the elbow starts to read as a sleeve that was meant for someone taller, and anything much above mid-bicep changes the register of the garment entirely.
The test: slide two fingers flat between the sleeve opening and your arm. Flat, side by side, not stacked. They should go in without effort and without swimming. A ribbed cuff will grip a little more than a plain hemmed one, and that light grip is the cuff doing its job. A cuff that leaves a mark on your arm after ten minutes is a size too small.
How should a shirt fit length
Length is measured on the garment from the highest point of the shoulder straight down the front to the bottom of the hem. That is the number in a length column, and it is not the same as the distance from your own shoulder to where you want the hem to land, though the two are close enough to compare.
If a shirt is going into your trousers, length is forgiving. You want enough fabric below the waistband that it stays put when you sit down and reach forward, and no more. If it is staying out, length stops being forgiving and becomes the thing people notice first.
How should a shirt fit around the neck
On a classic buttoned shirt the test is old and it works: button the collar, then slide two fingers flat between the collar and your neck. Two fingers in comfortably means the collar is right. One finger means you will feel it by midday. Three means the collar will roll away from your neck and sit badly under a jacket.
A knit band collar cannot be tested that way, because it has no button at the throat and no fixed circumference. Judge it differently. The band should rest against your neck without pressing on it and without standing away from it. Swallow: if you feel the band move against your throat, it is tight. If you can see daylight all the way around, the band is too wide and it will lose its shape at the back within a month.
How should a shirt fit untucked
The rule is short and it holds almost everywhere: the hem covers your seat at the back and stops somewhere around the middle of your fly at the front. That is the window. Below it, the shirt starts reading like a nightshirt and shortens your legs in every photograph. Above it, you flash your waistband every time you reach for something on a high shelf.
Check it in a mirror with your arms down. The hem should land roughly between the base of your thumb and the middle of your palm. Then turn and look over your shoulder. If the back hem sits above the fullest part of your seat, the shirt is too short to wear out, whatever the front looks like.
Hem shape changes how that rule behaves. A straight hem is the same length the whole way round, so it draws a horizontal line across your hips and can be worn deliberately shorter, which is why boxy straight-hem tees look intentional at a length that would look wrong on anything else. A curved hem, the shirttail shape, is longest at the centre front and centre back and rises towards the side seams. It covers the seat without the sides looking long, and it stays tidy when you move.
One consequence catches people out. When a curved-hem garment quotes a length figure, that figure is taken at the longest point. Compare it to a straight-hem garment's length and you are comparing one garment's maximum to another garment's entire hem, so the curved one always measures longer than it wears. Expect roughly a couple of centimetres of difference at the sides.
Collar sizes in numbers: 37 to 44 and what they mean
On a classic buttoned shirt the size is a single number rather than a letter. 39, 41, 43. That number is the collar circumference in centimetres, taken along the collar band from the centre of the button to the centre of the buttonhole. It is not your neck measurement. It is your neck plus one or two centimetres of breathing room, already built in by the maker.
So a man with a 40cm neck buys a 41 or 42 collar, not a 40. Work out your own neck once with a soft tape or a calibrated charging cable, held level, sitting where a collar would sit rather than up under your jaw, and you never have to think about it again.
| Collar size (cm) | Usual letter size | Neck it usually suits (cm) |
|---|---|---|
| 37 | S | 35 to 36 |
| 38 | S to M | 36 to 37 |
| 39 | M | 37 to 38 |
| 40 | M to L | 38 to 39 |
| 41 | L | 39 to 40 |
| 42 | L to XL | 40 to 41 |
| 43 | XL | 41 to 42 |
| 44 | 2XL | 42 to 43 |
Treat that table as an approximation and never as a law. Two brands can hang the same 41 collar on bodies that differ by 6cm around the chest, because the collar is graded on its own ladder and the body is graded on another. Use the number to place yourself roughly on the scale, then use chest width to pick the actual garment.
It also does not apply to a knit band collar, and this is worth being blunt about. A band collar on a knit tee has no throat button, no fixed circumference and a rib that stretches under load and returns. Asking for a 42 in that garment is a question the garment cannot answer. That is precisely why our size guide is built on width and length rather than a collar number.
Height and weight as a starting point
Height and weight are the two numbers every man already knows about himself, which makes them a useful door into the problem. They are a starting point and not a promise, and any page that presents them as a guarantee is selling you certainty it does not have.
Read the table with one idea in mind: weight mostly moves the width, height mostly moves the length. That is why it has two axes instead of one.
| Weight | Under 175cm | 175 to 185cm | Over 185cm |
|---|---|---|---|
| 60 to 70kg | M | M | M or L |
| 70 to 80kg | M | M or L | L |
| 80 to 90kg | L | L | L or XL |
| 90 to 100kg | L or XL | XL | XL |
| 100 to 110kg | XL | XL or 2XL | 2XL |
| Over 110kg | 2XL | 2XL | 2XL |
Now the honest caveat: build beats both numbers. Two men at 85kg and 178cm can land two sizes apart. One of them carries the weight across his shoulders and chest and needs the width; the other carries it around the middle, where a shirt has plenty of room already, and swims in the same size. Shoulders and chest decide the letter. Weight only correlates with them.
Use the table to reach a candidate in ten seconds. Use the flat measurement to confirm it before you order. Ten seconds plus two minutes is still the fastest route to a shirt that fits.
Caught between two sizes
Being between sizes is a real position rather than indecision, and it deserves a real answer. Start by knowing what one step up actually buys you here: 2cm of width, which becomes 4cm around the chest once you double it, and 2cm of body length. That grade is identical on every colour we make, so the decision is the same whichever one you are looking at.
Decide on the shoulder, not on the chest. If the smaller size puts the shoulder seam on the corner of your shoulder, take the smaller one and accept a closer line through the body. If the smaller size drags that seam inward or pulls across your back, move up. A slightly loose body reads as a choice you made. A strained shoulder reads as the wrong size, and everybody can see it.
Two things tip the balance after that. What goes over the top matters: if it lives under a jacket, the smaller size keeps the line clean at the chest. And where you want the hem to sit matters, because 2cm of extra length moves the hem visibly against your belt line, which counts for a lot on a shirt you never tuck in.
The numbers on this shirt
Everything above is general and applies to any shirt you own. This part is specific to what we make, and one thing in it surprises almost everyone.
Black runs 4cm shorter in the body than Cream and Heather Grey at every size. Crimson sits between them, 2cm shorter than Cream and Heather Grey. Same letter, same width, different length. So read the row for the colour you are actually buying rather than the row for the size you usually take. Publishing four separate sets of numbers is more work than publishing one, and the reason we do it is the same reason behind everything else on the about page: one garment, measured honestly, described exactly.
| Colour | Size | Width (cm) | Length (cm) |
|---|---|---|---|
| Black | M | 55 | 68 |
| Black | L | 57 | 70 |
| Black | XL | 59 | 72 |
| Black | 2XL | 61 | 74 |
| Cream | M | 54 | 72 |
| Cream | L | 56 | 74 |
| Cream | XL | 58 | 76 |
| Cream | 2XL | 60 | 78 |
| Heather Grey | M | 54 | 72 |
| Heather Grey | L | 56 | 74 |
| Heather Grey | XL | 58 | 76 |
| Heather Grey | 2XL | 60 | 78 |
| Crimson | M | 55 | 70 |
| Crimson | L | 57 | 72 |
| Crimson | XL | 59 | 74 |
| Crimson | 2XL | 61 | 76 |
Width is underarm seam to underarm seam, so double it to compare with your own chest. Length runs from the highest point of the shoulder straight down to the hem, taken at the longest point of the curve. The cut is a regular fit with a little room through the body, it runs M to 2XL, and every colourway is stocked in all four sizes. The same numbers sit permanently on the size guide page, so you never have to come back here to find them.
One local reason to take the extra two minutes: everything here ships cash on delivery. A size that has to go back is a parcel that travels twice and gets paid for once, which is worse for you than a card refund and worse for us than almost anything else. Measuring a shirt you already own removes most of that risk before it starts. If the numbers line up, the shirt these measurements belong to is one page away.
The rest of The Code deals with what to wear and when. This piece deals with whether it will fit, which has to come first.
How do I know my shirt size without a measuring tape?
Use a sheet of A4 paper. Its short edge is exactly 21cm and its long edge is 29.7cm. Lay a shirt that fits you flat, run the paper across from one underarm seam to the other, and count. A bank card works the same way at 8.56cm per length. Compare whatever number you get to the width column in the size guide.
Should I size up if I am between two sizes?
Let the shoulder decide. One step up adds 2cm of width, which is 4cm around the chest, plus 2cm of length. If the smaller size puts the shoulder seam on the corner of your shoulder, keep it and live with a closer body. If the seam pulls inward or the back feels tight when you reach forward, take the larger size. A relaxed body is a style choice, a strained shoulder is a mistake.
Does the same size fit the same in every colour?
Not on this garment, and we would rather say so plainly. Black is 4cm shorter in the body than Cream and Heather Grey at every size, and Crimson sits 2cm shorter than those two. The width is unaffected, so the change is entirely in how far the hem falls. If you switch colours, check the length row before you assume your usual size carries over.