Weathering indices can be used to quantify weathering of rocks at various stages of weathering processes and provide a better understanding of element mobility during weathering. Various weathering indices have been proposed in the literature worldwide. In the present work, radioactive secular disequilibrium has been used to determine weathering extent. Thirty-seven samples from Kavala and thirty from Sithonia beach sands, all of them being the weathering products of the local granitic plutons, are studied for their secular disequilibrium in both 238U and 232Th series (226Ra/238U and 228Ra/228Th respectively). The results are compared to weathering indices already in use worldwide and suggest a consistent correlation with WIP (alkaline and alkaline-earth element leaching) and PWI (silica leaching) for the well and very well sorted sands and for the heavy minerals of Kavala. This study suggests that with an appropriate choice of the weathering index and samples both U-series and weathering index can recover the extent of chemical weathering.