Tolerance

Tolerance is the margin a finished garment is allowed to differ from its specification. The spec sheet gives a target for each measurement of each size; the tolerance says how far above or below it a piece can measure and still pass. Each brand and factory sets its own.

Some difference is unavoidable. Fabric shrinks or relaxes, seams are sewn by people, and a knit lies a little wider or narrower on the table depending on how it is smoothed. Two shirts of the same size, off the same line, rarely measure exactly alike.

On a size chart

A garment chart gives one number per size: the target. Ruban Size's men's T-shirts template says the M is 53 cm across the chest, laid flat. A shopper who measures the shirt at home and finds a slightly different number hasn't found a mistake, only the tolerance.

Two habits keep it small on your side. Measure your samples the same way on every size: flat, buttoned, smoothed without pulling, as in how to measure a garment flat. And give body charts ranges rather than single values: a chest of 90 to 95 cm says where an M starts and stops without pretending to a precision no garment has.

In Ruban Size

Find my size doesn't treat the edge of a range as a wall. Where two printed ranges leave a gap, as between the M (90-95 cm) and the L (96-102 cm) of the women's tops chest, the boundary sits halfway, at 95.5. A measurement near it gets an answer like "You are between M and L. We suggest M.", with the neighbor size when it is a real alternative. The confidence (high, medium or low) is the chance that typical measuring error keeps every measurement that matters inside the chosen size, so it drops near a boundary. For shoe widths, a foot within half a centimeter of the chart's width counts as regular.