Our Accuracy Method

Most sizing sites copy a conversion table from somewhere else. That's exactly how wrong numbers spread across the whole web — one site's rounding error becomes everyone's. We don't do that.

We derive, we don't copy

247Sizing computes every size from foot length (or finger circumference, or body measurement) using the published geometric systems — Mondopoint (ISO 9407), the Paris-point scale behind EU sizes, the barleycorn scale behind UK/US sizes, and ISO 8653 for rings. The physical measurement is the anchor; the size is derived from it. That makes the whole thing transparent and correctable rather than a black box.

We're honest about variance

Real-world fit varies in two places, and we expose both rather than hide them. Manufacturing ease — how much room a maker builds in over the bare foot — differs between athletic and dress lasts. And brands cut consistently small or large: we name them (Converse runs large, Clarks slightly large, Birkenstock uses EU only) instead of pretending a single number is the final word.

What we will never do

We don't invent precise conversions we can't stand behind, and we don't present a derived estimate as gospel. Where a system is genuinely approximate — the cm-based Japanese, Chinese and Mexican scales, for instance — we say so. The goal is the most accurate honest answer, plus the one instruction that beats every chart: measure first.