For a sample of 404 F- to M-type stars we created the largest sample of simultaneous X-ray and CaII H & K observations of late-type stars obtained so far to study the correlation between different activity indicators. We compare X-ray fluxes measured within the first all-sky survey conducted by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) instrument on board the Spectrum-Roentgen-Gamma (SRG) observatory to CaII H & K excess flux measurements, using observations made with the robotic TIGRE telescope.