The radioradius of the Sun is an important and suitable observational feature that connected with structure of the atmosphere. Its value in millimeter and submillimeter range defines the chromospheres height (limb extension). Numerous measurements of the solar radioradius provide ample opportunities for testing models of a solar atmosphere comparing observational and model values. Special interest causes a millimeter-submillimeter range of
wavelengths, radiation in which is completely defined by chromosphere. In the presented work model calculation of radioradius for spatially-non-uniform 3D models of chromosphere by means of program Bifrost for a cube 24×24×17 Mm with spatial resolution of 48 km across and 19–100 km on a vertical is executed. Values of radioradius were calculated for set of wavelengths from operating range of ALMA radiointerferometer. Comparison of observational and modelling values shows that the measured values of radioradius significantly surpass calculated on the used numerical model. In the considered range the measured radioradius changes from 7" up to 24" while model calculation gives the values which are not exceeding 3". Such strong discrepancy requires additional research.