That’s about the size of it
Definition 1 of 1
Pro Tip 1/3Informal Usage
Use it in casual conversations rather than formal or professional settings. 
You ate all the cookies, and now there's none left for me? Sounds like that's about the size of it.
Pro Tip 2/3Confirmation Seeker
'That’s about the size of it' can suggest you're seeking confirmation or agreement from others. 
So, the party will be postponed if it rains, that's about the size of it, right?
Pro Tip 3/3Summary Statement
It's often used after explaining something to summarize the main point. 
I explained the rules: no running, no shouting, and no chewing gum. That's about the size of it.