Measures: Length — how far or how big
Metre
The base unit of length — about one long step.
LengthHow it's defined
Since 1983, the metre is the distance light travels in a vacuum in 1/299,792,458 of a second. That fixes the speed of light exactly and makes the metre as stable as the second it is built on.
Convert — honestly
39.3700787 in
Inch · factor exact — exact by the 1959 yard-and-pound agreement
3.2808399 ft
Foot · factor exact — exact by definition
0.000621371192 mi
Mile · factor exact — exact by definition
Conversions run through the metre using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
- Venuii — room dimensions and stage plots ↗ open venuii
- Every tape measure outside the US, and all of science inside it
Source
This page is an authored summary of the authoritative definition — checkable one click away.
BIPM — The International System of Units (SI Brochure, 9th ed.)