It used to be 2 spaces but nowadays it is only 1.
no spaces
2 Spaces
In typing, proper style is 2 spaces after a period (.), as well as after a colon (:).
one
2
2
one space after and abberviation two spaces at the end of a sentence
One space follows a period after an initial.
One.
1
How many spaces do you need after the word period? Is she having her period.
One space between words. No space between the last word and the period or interrogative. Two spaces after the period or interrogative.