The current star formation rates (SFR) for a sample of 8156 star-forming galaxies from the Sloan Digital Sky Survey (DR4) are derived using the following estimators: the galaxy far-infrared luminosity (the IRAS data, N = 350), the monochromatic luminosity in the radiocontinuum at 1.4 GHz (the NVSS data, N = 475) and H_α emission of ionized hydrogen regions (corrected for interstellar extinctions and aperture, N = 7006). The Salpeter shape of the initial mass function with the mass range from 0.1 to 100 M_☉ was assumed for SFR_FIR calculations. The SFR_1.4 was determined assuming that the fraction of thermal component in the galaxy radiocontinuum emission at 1.4 GHz is about 10 %. The upper limit of starburst age is estimated for galaxies with known abundances of heavy elements. The results are compared with similar studies for H II Markarian galaxies and isolated ones.