First of all vs For one thing

When to use each in English, with meaning, register, and examples.

First of all

Top 2,000 (common)

For one thing

Top 3,000 (common)

Most common: First of all

	First of all	For one thing
Pronunciation	🇬🇧 //fɜːst əv ɔːl// 🇺🇸 //fɜrst əv ɔl//	🇬🇧 //fɔː wʌn θɪŋ// 🇺🇸 //fɔr wʌn θɪŋ//
Meaning	To start with; the first point to mention.	One reason or point to consider.
Example	First of all, we need to discuss the budget for next year.	For one thing, it’s cheaper to travel by bus.
Register	Neutral	Neutral
How common	Top 2,000 (common)	Top 3,000 (common)
Collocations	first of all, we need, first of all, let's discuss, first of all, thank you, first of all, I want to, first of all, remember	for one thing, for one important thing, for one specific thing
Common mistakes	Using it in the middle of a sentence instead of at the beginning., Confusing with 'firstly', which is more formal., Omitting 'of all' and saying only 'first'.	Using it without context, making it unclear., Incorrectly following it with unrelated statements., Confusing it with similar phrases like 'for one reason'.
Usage notes	Often used to introduce the first point in a list. Appropriate in both spoken and written contexts. Avoid in very formal settings.	Use this phrase to introduce a reason or point in discussions. It's often used informally but can be appropriate in more serious contexts as well.

See it in real clips

Avengers › Avengers Endgame

First of all, that's horrible.

Agatha Christies Poirot › S1 E1

First of all. . .

Yes. First of all, you're all done.

Avengers › Avengers Endgame

First of all, that's horrible.

Agatha Christies Poirot › S1 E1

First of all. . .

First of all

Avengers › Avengers Infinity War

Well, for one thing, I'm not asgardian.

For one thing

Frequently asked questions: First of all vs For one thing

What's the difference between First of all and For one thing?

First of all: To start with; the first point to mention. For one thing: One reason or point to consider.

Which is more common: First of all and For one thing?

First of all is the most common in everyday English.

Can you show an example of each?

First of all: First of all, we need to discuss the budget for next year. For one thing: For one thing, it’s cheaper to travel by bus.

Can I use First of all and For one thing interchangeably?

Not always. First of all and For one thing are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.