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The detection of Earth-mass exoplanets in the habitable zone aroundsolar-mass stars using the radial velocity technique requires extremely highprecision, on the order of 10$\,$cm$\,$s$^{-1}$, below the intrinsicvariability of even relatively inactive stars, such as the Sun. One suchvariable is convective blueshift varying temporally, spatially, and betweenspectral lines. We develop a new approach for measuring convective blueshiftand determine the strength of convective blueshift for 810 stars observed bythe HARPS spectrograph, spanning spectral types late-F, G, K, and early-M. Wederive a model for infering blueshift velocity for lines of any depth inlater-type stars of any effective temperature. Using a custom list of spectrallines, covering a wide range of absorption depths, we create a model for theline-core shift as a function of line depth, commonly known as the thirdsignature of granulation. We utilize an extremely-high-resolution solarspectrum (R$\sim$1$\,$000$\,$000) to empirically account for the nonlinearnature of the third signature. The solar third signature is then scaled to all810 stars. Through this we obtain a measure of the convective blueshiftrelative to the Sun as a function of stellar effective temperature. We confirmthe general correlation of increasing convective blueshift with effectivetemperature and establish a tight, cubic relation between the two that stronglyincreases for stars above $\sim$5800$\,$K. For stars between $\sim$4100$\,$Kand $\sim$4700$\,$K we show, for the first time, a plateau in convective shiftand a possible onset of a plateau for stars above 6000$\,$K. Stars below$\sim$4000$\,$K show neither blueshift nor redshift. We provide a table thatlists expected blueshift velocities for each spectral subtype in the data setto quickly access the intrinsic noise floor through convective blueshift forthe radial velocity technique.

Convective blueshift strengths of 810 F to M solar-type stars