Band resistance, which is a curve and not a weight

What the convention fixes

Almost nothing, and that is the point worth making plainly.

A band’s rating is a force, usually printed in kilograms or pounds, that the band exerts at some extension. What extension is the crucial variable, and it is the one listings routinely omit. A band described as 15 kg might reach that at double its resting length, at triple it, or at a figure nobody wrote down.

The colour code that accompanies the rating fixes nothing at all across brands. It is a house ordering — lighter to heavier within one maker’s range — and it carries no meaning between ranges.

What it does not promise

It does not promise a constant load. The whole behaviour of an elastic is that resistance rises as it stretches; a rep performed with a band is loaded least where the movement starts.

It does not promise comparability between brands, between lengths, or between looped and tubed constructions.

It does not promise anything about durability. Latex ages, and it ages faster in sunlight, in heat and against rough concrete. A rating is a property of a new band.

And on this shelf specifically, it does not promise the figure was measured at all. Many listings inherit a range from the factory sheet without any published method behind it.

What it works with

It works with the resting length a maker publishes, because a rating without a length is a rating without its denominator.

It works with the width and thickness on looped bands, which are the dimensions that separate two bands sharing a colour.

And it works with what the band is anchored to, which on suspension trainers and door anchors is a separate published figure and is frequently the real limit.

How we read it on this site

Ratings are reported exactly as the maker publishes them — the range, the unit, and the colour name if the maker uses one — and the page says whether an extension is specified. Where it is not, the page says the figure is a point on an unstated curve, which is the true reading.

No page here converts a band rating into an equivalent weight, and none ranks bands by their printed numbers alone. Where a set is compared, it is compared on the lengths, the dimensions and the construction, because those are the figures that were actually measured.