Determine final guage?

How does one determine the final guage of a conductor, when it is stated that it is made of, for example, "...5 strands of 16 guage wire..." or, "...6 strands of 18 guage wire..." or something to that effect? In each respective case, I do not believe the final conductor would still be 16 or 18 guage, correct?
Any help in clarifying this would be appreciated.
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Double the number of conductors, go up 3 sizes.
when a company says their power cable is 10 gauge, does that mean the total gauge of all 3 conductors is 10 or each of the 3 conductors are 10 gauge?
Yo2tup, Using Tvad's sleeve calculator would imply that the total of all 3 gauges makes it a 10 gauge. If each conductor is 10 gauge, per the sleeve calculator, it would be considered a 6 gauge wire. Hey Tvad thanks for the calculator!!!