If a player is sent off, it is a matter of fact the player will be suspended 7 days after the date of the game, as set out by The FA in the Discipline Regulations.
The length of ban depends on the type of misconduct:
Serious Foul Play
3 match suspension
5 penalty points
Violent Conduct
3 match suspension
6 penalty points
Spitting at an opponent
6 match suspension
7 penalty points
Denies an obvious goal scoring opportunity by an offence punishable by a free kick or penalty kick
1 match
3 penalty points
Denying an obvious goal scoring opportunity by deliberately handling the ball
1 match
3 penalty points
Use of offensive, or insulting or abusive language
2 matches
4 penalty points
Receiving a second caution in a match
1 match suspension
3 penalty points
The above sanctions only apply if it is the participants first red card in a specific category of football for the current playing season. An additional match will be added to the suspension for each previous sending off in the same category of football in the current playing season.
You can read more about misconduct charges in the Discipline Handbook.
A link to the most up-to-date version of The FA Handbook can be found below.