The end tab

Many sewing and tailor's tapes finish their end in a small folded metal tab, meant to stop the tape fraying and to give something to grip. The tab is not the zero point - the printed "0" sits a short distance in from the tab's own edge on most tapes, and treating the tab's edge as the start of the scale adds that gap to every reading.

Why the tab exists and why it is not zero

The metal tab is a manufacturing detail, added for durability on a tape that gets pulled taut repeatedly in dressmaking use, not a measuring feature. On tapes designed for wrapping around an object and reading where the tape crosses back over itself, the tab's presence does not matter, because zero is wherever the printed scale says it is, not wherever the material ends - the overlap method never asks where the physical tip is. The tab only becomes a problem if you are, instead, holding the tab's edge against a landmark and reading the number where the tape reaches around, treating the tab's physical end as though it were the zero mark.

How to find the real zero

Look closely at the printed scale near the tab. On most tapes the "0" is printed a few millimetres in from the tab's outer edge, sometimes with a small arrow or line marking the true start. If you are using the tape by wrapping it around the shaft and reading the number that lines up where it crosses the starting point - the standard technique - the tab's exact position never enters into it, because you read the number directly at the overlap rather than counting from the tab. The tab only matters if you are, for some reason, trying to use the tape held flat with the tab pressed against a fixed edge, which is closer to how a rigid ruler is used and is not the technique this instrument is built for.

The safer habit

The overlap method - wrap, mark where the tape crosses itself, read the number at that mark - sidesteps the tab question entirely and is the more reliable technique regardless of tab position, which is also how girth is read in the standard method. If you do find yourself needing to read from a fixed end for any reason, confirm the printed zero position once, the same way you would check where a rigid ruler's own zero sits, rather than assuming the tab's edge is the start.

Why this is easy to get wrong the first time

Nobody sets out to measure from the tab on purpose - it happens because the tab is the first solid thing your fingers find when you pick the tape up, and pinning it against a landmark feels like the natural way to hold a fixed starting point. The overlap method avoids this trap entirely, but if you have previously used the tape held flat with the tab pinned against something, it is worth checking whether any of those readings need revisiting, since the tab offset on most tapes runs from one to a few millimetres - not large, but not inside the noise of a careful reading either.

Once you have found the printed zero on a given tape, it does not move, so this is a check you make once per tape rather than every session. A small pen mark next to the printed zero, if the tape is one you will use repeatedly, saves having to hunt for it again next time.

Same category of error, different instrument

This is functionally the same problem as a ruler whose scale starts inside its own physical edge, just on a tape instead of a rigid ruler, and it is worth checking on any new tape once rather than assuming - a habit that also applies to distinguishing a proper tailor's tape from a builder's tape, which has an entirely different and worse zero problem of its own.

None of this touches a photograph-based rating, where no physical tape or tab is involved at all. Rate Cock scores an image rather than reading a tape, and the same holds for a photo-based tool, a human judge's opinion, and an AI model's inference from a picture - a metal tab on a sewing tape is not a variable any of them ever encounters.