We leverage the high resolution and spectral stability of the Keck Planet Finder (KPF) spectrograph to investigate macroturbulence broadening via the stellar cross-correlation function (CCF). As our calibration sample, we use main sequence benchmark slow-rotators vsini < 4 km/s where rotation rates were derived from the most robust asteroseismic mode splitting measurements, independent from spectral line broadening. We fit a linear relationship for macroturbulence as a function of derived νₘₐₓ, the frequency of maximum power due to stellar oscillations, with an RMS scatter of 90 m/s. Previous studies have calibrated macroturbulence against T_eff, but we find νₘₐₓ to be a lower dispersion predictor by a factor of 4 indicating a deeper relationship between νₘₐₓand convective motions.