Big-Large | Commonly Confused Words

Big

/bɪɡ/

Large in size, extent, or capacity.

I think Tom made a big mistake.She gave him her biggest smile.Perhaps I will, when I'm bigger.'

/lɑːdʒ/

Of a size greater than the usual or average

"They have the largest babies' sizes."This left larger portions of real money for the others.'How large were the footprints?

Think of big as more informal and common in everyday speech, while large is often used in more formal contexts.
Both big and large describe size but large can also imply volume or extent in a more quantitative way.
You might use big for abstract ideas like big plans, whereas large is more likely to be used for physical dimensions such as large room.