You did the work. You measured a garment you own, found the chart for the exact item, lined the numbers up, and your figure landed between two rows.
This page is only about that moment. It is not about how to measure — that walkthrough already exists — but about what to do when the measuring is done and the table refuses to answer.
Before anything else, check whether the chart can answer
The first question is not "which size". It is whether these two sizes are actually distinguishable on paper.
We hold 57 charts from one seller, MVT, published beside the items on the shelf. Between them they contain 148 pairs of adjacent sizes, and 56 of the 57 print the seller's own admission of measurement error, usually one to three centimetres.
Compare each adjacent pair field by field and ask whether anything separates them by more than that admitted three centimetres. In 118 pairs, something does. In 30 pairs — roughly one in five — nothing does.
When you are in one of those 30, the chart has not given you a close call. It has told you it cannot resolve the question. Stop reading the table and start deciding on something else.
The field that separates them is rarely the field you were looking at
Across those 148 pairs, here is which field does the work of telling two sizes apart by more than three centimetres:
- Waist: 95 pairs out of 95. Every single adjacent pair on every lower-body chart steps by exactly four centimetres.
- Hip: 86 pairs out of 93.
- Chest: 19 pairs out of 55.
- Shoulder: 5 out of 55.
- Leg opening: 2 out of 93.
- Sleeve: 0 out of 51.
- Length: 0 out of 148.
So on anything with legs, the waist always decides and it always decides cleanly. On anything with sleeves, the chest decides about a third of the time and nothing else meaningfully does. Shoulder and sleeve are constraints, not tiebreakers, and length never breaks a tie in this entire corpus.
Which means the practical version of "I am between sizes" is usually: I am between sizes on the chest, and there is no second opinion available on the card.
The ladder, in order
When the table genuinely cannot resolve it, work down this list and stop at the first rung that gives you an answer.
- Fabric. Fifty of the 57 charts carry the seller's own instruction to rinse jeans in cold water only, which is a shrinkage warning written by the person selling the garment. Eleven name a composition — cotton, wool, polyester and linen blends appear. A heavy cotton that may shrink and a knit that will relax are two different bets, and they point in opposite directions.
- What you will wear under it. A chest measurement is not a fixed target. The layer you intend to put underneath changes it by several centimetres, and that is a decision the chart cannot make for you.
- Which failure you can live with. This is the honest tiebreaker. On a boxy or oversized cut, too big is wearable and too small is not. On anything cut close, both failures hurt, but the small one hurts more because it cannot be styled around.
- The seller's own body-to-size row. Forty-eight of the 57 charts print one. It is a weak signal and it does not transfer between items, but for this specific item it encodes how the seller expects the piece to sit, which is exactly the intent you are missing.
- Ask for the real number. Your agent has the item in a warehouse before it ships and can lay a tape across it. That figure comes off the object, not the card. It is also the last point where the answer changes anything.
Nowhere on that ladder is "size up". Sizing up is a rule of thumb borrowed from a market that grades sizes consistently, and the step arithmetic above is what happens when you check whether this one does.
Sometimes you are not between sizes at all
Occasionally the whole run sits on one side of you, and the letters tell you nothing about that until the item lands:
I got a size XXS and it's still oversized but the fit is great!
u/maerkeligt, r/FashionReps, 27 September 2019
That is a buyer at the smallest size a store offered, still swimming in it, and pleased about it because the cut was meant to be worn that way. Read it as a warning about the opposite case: if the largest size on the chart is close to your reference rather than comfortably past it, being "between L and XL" is not your problem. Running out of chart is.
The check that catches a wrong call anyway
There is one more reason to treat the chart as provisional rather than decisive, and it is not hypothetical:
Not great on the T-shirts, quality is standard some were missing care labels, the sizing was awful ordered medium by the size chart, when it got to agent it was 5cm longer I said and rainbow reps said it will be ok. It arrived and it’s more like XXXL goes to my knees nearly.
u/Only_Bluebird8483, r/FashionReps, 26 January 2026
Read the sequence rather than the verdict. A size was chosen from a chart. The agent's photos showed a five-centimetre discrepancy. The discrepancy was raised, reassurance was given, and the parcel shipped. The information arrived in time; the decision to act on it did not.
That is the whole argument for the fifth rung of the ladder. The measurement at the warehouse is the only one taken from your actual item, reading QC photos is where you learn to ask for it, and a five-centimetre gap between the card and the object is a reason to change the order rather than a detail to be talked out of.
Fifty-seven charts is a narrow base
Fifty-seven charts from one store is a narrow base, and none of these garments were bought and re-measured by anyone here. What generalises is not the numbers but the test: take the gap between your two candidate sizes on the field that matters, put it next to the tolerance the seller printed on their own chart, and see which is larger.
If the tolerance wins, the chart is not making your decision. You are — so make it on fabric, on layering and on which mistake you would rather wear.