Everything, from the 100m time to the height in pole vault, has to be converted into points, that make up the final score in a decathlon. To do that, there are exact formulas and scoring tables.
This handy combined events points calculator allows you to calculate both of men's and women's decathlon, heptathlon and pentathlon scores. Also adjust for junior competitions.
I wish that in the nearest future everybody will know about decathlon and the meaning of the event of decathlon... decathletes are like our greek gods - Petros Kyprianou