Exclude null value in average

I am averaging a column of 10 numbers. Some cells are blank (no value). Excel provides average for the cells that have a value only. For example, of the 10 averaged cells, 2 are blank (no value) Instead of averaging on 10, Excel averages on 8.

How do I set up the formula to calculate on the 10 cells?

Thanks for your help.

=sum(a1:a10)/10
?