Kinship analysis using DNA typing plays an important role in the identification of an unknown decedent. We have developed a tool based on Microsoft Office Excel to support kinship analysis. The tool calculates likelihood ratios (LRs) based on Wenk's equation when the STR (short tandem repeat) types of the unknown decedent and those of the alleged relative are entered. We validated the tool by calculating LRs for 100 cases of unknown person-alleged child relationships and 100 cases of unknown person-alleged sibling relationships. The values of the LRs calculated with this tool were consistent with those calculated using the DNA-VIEW software. Further, the distribution of the LRs was almost the same as the distribution of simulated LRs in paternity and sibling tests reported in a previous study. This tool should expedite the fast and efficient identification of an unknown decedent.