My goal for this chapter, based on a series of lectures at the XXIII Canary Islands Winter School of Astrophysics, is to present current understanding and calibrations of star formation rate (SFR) indicators, both on global, galaxy-wide scales, and on local, sub-galactic scales. SFRs are, together with masses, the most important parameters that define galaxies and their evolution across cosmic times. Although SFR calibrations have existed, with various levels of accuracy, for many years and sometimes decades, the past eight to ten years have brought forth major progress, through cohesive, multi-wavelength surveys of nearby and distant galaxies. These surveys have exploited the sensitivity, angular resolution and/or large field of view of space telescopes (e.g., the Spitzer Space Telescope, the Galaxy Evolution Explorer [GALEX], the Hubble Space Telescope [HST], and the Herschel Space Telescope) and leveraged the multi-band coverage supplied by ground-based, all-sky surveys (e.g., the Sloan Digital Sky Survey), in order to push the definition of SFR indicators into new regimes, both in terms of wavelength coverage and spatial scales. I review here recent progress in this area, but also highlight where challenges, sometimes unexpected ones, have arisen. This chapter is structured to provide also a quick reference for the relevant literature on SFR calibrations. It loosely follows the structure of the lectures I presented at the Winter School.