Universal Length Converter

The span this page covers runs from a millimetre to the astronomical unit, ten columns wide, all pivoting on the metre. Several of its constants are exact by definition rather than measured: the nautical mile is precisely 1852 m, fixed by international agreement to approximate one minute of arc along a meridian, and the astronomical unit has been frozen at exactly 149,597,870,700 m since IAU Resolution B2 redefined it in 2012 instead of tying it to Earth's orbit. The statute mile is 1609.344 m, the inch 0.0254 m, and the yard 0.9144 m — all exact under the 1959 international yard-and-pound agreement documented in NIST's own SI conversion guide (Special Publication 811), which is why the imperial columns here carry no measurement uncertainty of their own.

The retired US survey foot, two parts per million longer, is not offered; that gap is invisible on a workbench and material across a township boundary. A few practical limits: entry is decimal only, so a fractional inch has to be typed as 0.375 rather than 3/8, and every column is rounded to nine decimal places before it is displayed, which pushes the astronomical-unit result to a hard zero for any terrestrial distance rather than merely a small number. Light-years, parsecs and angular measures such as mils are outside the table entirely.