We present a method to combine CryoSat-2 (CS-2) radar altimeter and Sentinel-1 synthetic aperture radar (SAR) data to obtain sea ice thickness (SIT) estimates for the Barents and Kara Seas. Our approach yields larger spatial coverage and better accuracy compared to estimates based on either CS-2 or SAR alone. The SIT estimation method developed here is based on interpolation and extrapolation of CS-2 sea ice thickness (SIT) utilizing SAR segmentation and segmentwise SAR texture features. The SIT results are compared to SIT data derived from the AARI ice charts, to ORAS5. PIOMAS and TOPAZ4 ocean-sea ice data assimilation system reanalyses, and to daily MODIS based ice thickness charts. Our results are directly applicable to the future CRISTAL mission and Copenicus programme SAR missions.