The limiting fictive temperatures (Tf′) of 16 multi-component silicate glasses have been derived quantitatively from heat capacity measurements, following the method of Moynihan et al. (1976). These quantitative values of Tf′ closely match temperatures corresponding to the onset (Tonset) of the rapid rise in dilatometry heating curves (dL/L vs. T) at the glass transition, obtained on glasses with similar cooling histories. The mean deviation (Tf′− Tonset) is 5 K, whereas the maximum deviation is 17 K. These results confirm that the Tf′ of a silicate glass can be determined from the Tonset of a glass dilatometry curve with an uncertainty that is <20 K. An application of the Tf′ measurements includes the precise determination of the specific volumes of supercooled liquids at their respective Tf′ values (Lange 1997). By comparison with other measurements in the literature, the accuracy of the Tf′ method for determining low-temperature, fully relaxed, supercooled liquid volumes is shown. A comparison of volume-temperature models in the literature shows that a linear model (where thermal expansivity is independent of temperature) provides a superior fit of measured volumes in the SiO2-Al2O3-MgO-CaO-Na2O-K2O system over very wide temperature intervals (700–1900 K).