what percentage of human sperm cells carry an x chromosome
This means the chromosome number 23, that half of the sperm contain an X and half of the sperm contain a Y. Roughly 50%. The egg has an X chromosome. The sperm contributes either an X or a Y. If there are two Xs, then the baby will be female. If XY then the baby will be male. Since about half of all babies are female (slightly more than half), I'd say about half of all sperm carry the X chromosome.