The question regularly comes up: One space or two after a period? At The Proofreaders, we firstly abide by our clients’ style sheet or standard style sheet, such as APA, CMOS, AMA, etc. If the client does not have/provide a style sheet, we abide by the rules found in Jane Strauss’s Blue Book of Grammar.
We were always taught to put two spaces after each period, not one. Thanks to The Atlantic, we see that two spaces is the preference.
Here is an article demonstrating this belief:
One Space or Two