Newb Question Regarding Refinance

[Robin Morales]

Hi BP,

I apologize for the newb question.

Scenario:

Current loan

20yr fixed

Years Left: 18

Loan: 235,000

Current rate: 4.375%

Refinance Loan:

15-Year Fixed Rate

Loan Amount plus closing costs: $215,000.00

Interest Rate: 2.875%

APR: 3.070%

What is the best way to know whether or not a refinance should be done ?

How is the math done ?

I appreciate all of your help!!!!