Does Sizing Up Actually Add Length? I Measured the Same Shirt in Two Sizes

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Sizing up is the thing every tall man does when a garment is too short. You go up a size hoping the extra fabric lands where you need it. Sometimes it does. Mostly it goes somewhere else.

I own the same Under Armour exercise shirt in 3XLT and 4XLT. (If you want a cheaper tall performance tee, the Amazon Essentials two-pack is the one I measured and reviewed — a different shirt from the one below, and cheaper.) Same brand, same garment, one size apart. That is the cleanest test of sizing up I have, because nothing else changes — not the pattern, not the fabric, not the maker. Here is exactly what that one step bought.

One size step, measured

Measurement	3XLT	4XLT	What the step added
Body length, back	32.5 in	35 in	+2.5 in
Chest, around	56 in	61 in	+5 in
Sleeve, centre back to cuff	21.5 in	23 in	+1.5 in
Sleeve opening, flat	8.5 in	9.25 in	+0.75 in

Read the last column rather than the first two. You buy five inches of width to get two and a half inches of length. That is the trade, and nobody tells you it is a trade.

Sizing up is not a length adjustment. It is a width adjustment that happens to include some length.

Why that ratio matters more than the numbers

If you are tall and broad, this is a good deal. You wanted both, you got both, and the garment now fits in two directions instead of one.

If you are tall and lean, it is a bad one. You needed the 2.5 inches. The 5 inches around the chest is fabric you did not want, and it is why a sized-up shirt hangs like a bin liner while still finishing above your belt. The length problem gets partly solved and a new problem arrives with it.

The compression tights I measured show the same grading logic from the other end — generous on girth, mean on length — and they are on Amazon if you want to check the numbers against a pair in your hands.

This is the whole reason tall sizing exists as a separate thing. A tall size adds length and leaves girth alone. Sizing up adds girth and throws in some length. They are not substitutes, and the second one is what most brands leave you with because they never made the first.

Where sizing up works, and where it does not

If you are…	Does sizing up help?
Tall and broad, in activewear	Yes. Both dimensions were short and both got longer.
Tall and lean, in activewear	Partly. You gain the length and inherit width you did not ask for.
Buying knitwear	Probably not — see the caveat below.
Buying a woven shirt or trousers	No. Girth changes; body length and inseam barely move. This is what tall sizing is for.

The knitwear caveat, stated honestly

I measured two sweaters — an Amazon Essentials in 2XL Big-Tall and an Izod in 3XLT. Their body lengths land within half an inch of each other despite the nominal size difference, which suggests knitwear grades length far more meanly than active wear does.

But those are two different brands with two different size systems. That is not the same test as the shirt above, and I am not going to present it as one. The active wear number is measured. The knitwear number is an observation waiting on a proper test — the same sweater in two sizes, which I do not yet own.

I would rather tell you which of my own numbers I trust than round them into a tidier story.

What to do with this

• Measure the garment you already own and like. Body length back is the number. Everything else is noise until that one is right.
• If you are short by two inches or less in active wear, one size up will probably cover it — accept the extra width.
• If you are short by more than three inches, sizing up will not get you there. You need a tall size or a different brand.
• In knitwear and woven, do not expect sizing up to buy length at all. Buy tall or buy longer.

The garments these numbers came from

Everything above was measured on clothes I own. Where a piece is available I have linked it; where it is not, I have said so rather than sending you somewhere vague.

• Under Armour exercise shirt, 3XLT and 4XLT — the pair that produced the size-step numbers. I have owned these for years and washed them many times. Under Armour still sells the same shirt as the Tech 2.0. The measurements here are off the pair in my own drawer, not off a listing.
• Amazon Essentials performance t-shirt, two-pack — not the shirt measured above, but the tall performance tee I own that you can actually buy. Different brand, different pattern, and I have measured it separately. On Amazon · my review
• Under Armour compression tights, 3XLT — the same brand’s activewear grading, and the place the range runs out. On Amazon · full measurements
• Under Armour Tech Polo, 3XLT — the narrowest thing I own from them, and a good illustration of why sizing up is sometimes the right call. On Amazon · measured against two rivals
• Amazon Essentials cable knit sweater — one half of the knitwear comparison. On Amazon
• Izod sweater, 3XLT — the other half. On Amazon · both sweaters measured

If you want the shortlist rather than the reasoning, everything I actually recommend lives on Tall Deals, with the measurements behind each one.

Every figure here came off my own tape, on garments I own and wear. Nothing is read from a size chart.