How do you say I just had lunch in Mandarin?

There are a few ways to say "I just had lunch" in Mandarin, depending on the level of formality and context:

Formal:

* 我刚吃完午饭 (wǒ gāng chī wán wǔfàn) - This is the most common and formal way to say it. It literally translates to "I just finished eating lunch."

Informal:

* 我刚吃过午饭 (wǒ gāng chī guò wǔfàn) - This is a slightly less formal way to say it, similar to "I just had lunch."

* 我刚吃完 (wǒ gāng chī wán) - This is even more informal and simply means "I just finished eating."

If you want to emphasize that you just finished eating:

* 我刚吃完午饭 (wǒ gāng chī wán wǔfàn) - This is the most common and emphasizes that you've just completed the meal.

* 我刚吃完 (wǒ gāng chī wán) - This also emphasizes that you've just finished eating, but without specifying the meal.

The best way to say it depends on your situation and who you're talking to. If you're not sure, it's always safer to go with the more formal option.