This page explains that in the decathlon, every performance — ranging from sprint times to jumping and throwing results — is converted into points that determine the athlete’s total score. These points are calculated using official World Athletics formulas and standardized scoring tables.
It also highlights that there are several useful tools available for these calculations, including decathlon and heptathlon point calculators (such as Decathlon 2000), Excel-based scoring sheets, and other combined events scoring calculators.