As a preposition, do not place a comma in front of "for" unless using a particular sentence structure where commas are required.

We normally use "for" as a preposition—before a noun or a noun phrase (e.g., "I organized a surprise party for her birthday."). However, in very formal situations or literary language, we can use "for" as a coordinating conjunction to mean "because" or "since" (e.g., "I adore her, for she is the love of my life.")

As a preposition, do not place a comma in front of "for" unless you are using a particular sentence structure where commas are required.

I cooked a delicious romantic dinner for my girlfriend.

I cooked a delicious romantic dinner, for my girlfriend.

As a coordinating conjunction (as a synonym of "because" or "since"), use a comma before "for" to introduce an independent clause (a group of words with a subject and a verb that expresses a complete thought).

We must start saving money now, for life is full of unexpected events.

We must start saving money now for life is full of unexpected events.

1. Can You Use a Comma Before the Preposition "For"?

The preposition "for" can be used in a wide range of situations to describe:

• Benefits or the positive effects of something (e.g., "Regular exercise is great for your health.")
• Duration or period of time (e.g., "I've been working hard on this project for six weeks.")
• Helping someone (e.g., "I did some errands for my sister.")
• Use or function of something (e.g., "Use that hammer for driving nails into wood.")
• The reason behind something (e.g., "Mary is learning a new programming language for work.")
• etc.

We do not usually add a comma before the preposition "for":

Practicing yoga is good for your flexibility and strength.

This is a small fork for dessert.

There are particular situations, however, where you may need to use a comma before "for". For example, use commas to set off nonrestrictive information or add expressions that interrupt the sentence flow.

I've been living in Tokyo, without knowing a smidgen of Japanese, for five years.

2. When to Use a Comma Before "For"

In formal writing or literary language, the coordinating conjunction "for" can be used to introduce the reason for something (as a synonym of "because" or "since").

Thomas is a wise man, for he knows how to discriminate between good and evil.

If "for" introduces an independent clause, add a comma before it. An independent clause has a subject and a verb and can form a complete sentence standing alone.

Jennifer thought she had a good chance to get a promotion, for she has the right attitude and is good at her job.

Jennifer thought she had a good chance to get a promotion for she has the right attitude and is good at her job.

Commas with coordinating conjunctions

3. More Examples

3.1. 'For' as a Preposition (No Comma)

• My wife and I have been living in Detroit for two years.
• I made a chocolate mousse cake for your birthday.
• Forks are used for salad and splitting soft food into smaller pieces.
• Rebecca only paid 50 dollars for that dress.
• I love my girlfriend so much that I brought her chocolates and flowers for no reason.

3.2. 'For' as a Coordinating Conjunction (Comma)

• I believed Williams, for sure he would not lie to me.
• We listened to Peter actively, for he brought news of our loved ones.
• I know James is guilty of killing Patricia Brown, for I saw him do it.
• I feel better now, for I went to church and prayed to be nearer to God.
• Teachers are frustrated, for the government has cut wages in real terms for those who care for our loved ones.

4. Conclusion

Follow these quick guidelines to determine whether to use a comma before "for" in a sentence.

1. A comma before the preposition "for" is frequently unnecessary.
2. When using "for" as a coordinating conjunction (meaning "because" or "since"), place a comma in front of it to introduce an independent clause.