Extreme ultraviolet lithography (EUVL) at 13.5 nm will soon be applied in high-volume manufacturing of semiconductors, as a replacement to the ArF excimer laser immersion lithography. Recently, the potential application of exposure wavelengths of 6.x nm (particularly 6.6-6.8 nm) has been discussed as EUVL extension. The 6.x nm exposure source is currently under development, therefore screening of resists with conventional exposure tools will accelerate the selection or novel development of high sensitivity resists for 6.x nm EUVL. In the present study, the sensitivities of a chemically amplified (CA) resist (OEBR-CAP112) and non-CA resists (ZEP520A and poly(methyl methacrylate)) were evaluated with 30 keV and 75 keV electron beam lithography (EBL) tools. In terms of radiation chemistry, the obtained dose/sensitivities (μC cm-2) were converted into the absorbed doses (Gray; Gy = J kg-1). If EB- and EUV-induced chemical reactions are the same, the required absorbed doses for EB and EUV would be similar values. The sensitivities for EUV/soft X-rays including 6.x nm were predicted assuming the required absorbed doses in a resist would show similar values for both EB and EUV. We investigated precise sensitivities of the resists for EUV/soft X-rays including 6.7 nm using highly-monochromated synchrotron radiation. For both CA and non-CA resists, the predicted and experimentally obtained sensitivities agreed well with each other. These results suggested that almost the same chemical reactions are induced in resists for both EUVL and EBL. Hence, it was found that we can predict the resist sensitivities for EUV/soft X-rays at any exposure wavelength from the exposure results for EBL.