Proposal for a new CTOD calculation formula

•CTOD calculation from P–Vg curve was discussed using FE-analysis results.•The rotational factor, rp was newly calibrated and examined for the experiments.•A new CTOD calculation formula, considering yield-to-tensile ratio is proposed.•Prediction of numerical CTOD by the proposed CTOD was examined in wide range of YR.•The proposed CTOD calculation was also examined by the experiment results.