mm to inches converter
Enter a value in millimetres or inches and pick a direction — the conversion is exact, not rounded, because 1 inch is defined as precisely 25.4mm.
Result
0.9843 inches
This is the one converter on the site with no ambiguity or brand variance at all: millimetres and inches are both exact, internationally defined units, so the conversion is a fixed multiplication, not a chart.
United Kingdom
UK sizing sits between the two systems most UK shoppers actually order from: US retailers (Amazon.com, US-only brands) and EU ones (Zalando, ASOS' EU warehouses since Brexit changed cross-border returns). A UK 6 shoe, a UK M ring and a UK 34C bra are each a different number again once the label says US or EU — which is why three-way conversion gets searched here more than in most single-market countries.
Every conversion on this page runs in your browser. Nothing you type is uploaded anywhere.
Frequently asked questions
Is 1 inch exactly 25.4mm, or is that rounded?
Exactly. Since the 1959 international yard-and-pound agreement, the inch has been defined as precisely 25.4mm — not a rounded approximation of an older measure.
Why would I need this next to a ring or shoe size chart?
Ring circumference and shoe length are usually measured in mm or cm, but plenty of jewellery and footwear sold from US sites lists dimensions in inches — this is the plain unit conversion behind those charts.
Last updated: 2026-09-10