I am deciding between L and XL, so how should I take into account the 1–3cm margin of error in the size chart?

Let us place the numbers side by side first. For the ALLENO LLP Hoodie 01 Melange Grey, L has a total length of 73cm, chest of 70.5cm, shoulder of 63cm, and sleeve length of 55.5cm^[1]. XL has a total length of 75cm, chest of 73cm, shoulder of 65cm, and sleeve length of 58cm^[2]. Along with this, there is a note that a difference of about 1–3cm may occur depending on the measuring method^[3].

When these two notices are read together, the chart may seem meaningless, but they have different natures. Measurement error fluctuates in either direction, up or down, because values change slightly depending on the pulling force or reference points even when measuring the same garment again. On the other hand, the difference in values between L and XL is the result of the pattern being drawn differently in the first place, so all four parts increase in the same direction. Looking at only a single part, the difference might be buried within the margin of error, but the trend of the total length, chest, shoulder, and sleeve length increasing together does not get reversed just because the measuring method changes.

It is also good to factor in the fabric when making a judgment. This hoodie features a substantial, firm cotton^[4] with fleece added to the inside for extra warmth^[5]. Thick fabric does not drape along the body as easily as thin fabric, so it feels like there is less room even with the same dimensions, and layering a knit underneath in winter reduces chest and shoulder room first. Therefore, laying flat a hoodie you currently wear comfortably, measuring its shoulder and sleeve length, and comparing them with the numbers above will lead to a faster conclusion than simply staring at the chart.

hmmm, rather than being a phrase that blurs the chart, the mention of 1–3cm is closer to a signal telling you not to decide on a size based on a single number for a single part.