What a Litre of Vacuum Would Weigh: Mass Equivalents of Zero-Point Densities From a Bottle to the Observable Universe

Vacuum energy densities are usually left in energy units, where their sizes resist intuition. This paper converts three densities, the Planck-cutoff zero-point estimate, the electroweak-cutoff estimate, and the observed density of 2.52 x 10^-47 GeV^4, into gravitating mass equivalents inside four volumes from one litre to the observable universe. At the Planck cutoff, a litre of vacuum would carry a mass equivalent of 3.25 x 10^91 kilograms, about 5.45 x 10^66 Earth masses; at the observed density the same litre carries 5.85 x 10^-30 kilograms. The conversion is exact arithmetic from stated densities and is offered as a calibration of the vacuum hierarchy, not as a measurement.