A modified equation is proposed for the X-ray production range of 2-15 keV electrons in solids. The modification is obtained by an experimental procedure which compares the difference in X-ray intensities between pure element thin films and 'bulk' standards. The elements evaluated were Al, Ti, Ni, Zr, Nb, Mo, Pd, Ta and Pt. Monte Carlo simulations were made for several of the elements and agree with experimental results to within 5%. There was one exception, in the case of a high-atomic-number film (Pt on Si) at low keVs. Here the deviation increases to 10-20%. The modified equation is also compared to other range equations in the literature.