that's big of you

that's big of you

That is noble or commendable of you to do. This phrase is often said sarcastically. Wow, you're actually going to spend time with your brother tonight? That's big of you. That's big of you to reconcile with people who have wronged you in the past.
See also: big, of

that's big of you

used as an ironic comment on the meagreness of someone's generosity.
See also: big, of