Do the math
Definition 1 of 2
Pro Tip 1/3Think Carefully
It's about more than numbers; it means to consider all factors carefully. 
Before deciding on moving, do the math on the cost of living there.
Pro Tip 2/3Not Literal
'Do the math' isn't always about actual calculations; it's often used metaphorically. 
Weighing the pros and cons? Do the math and you'll make a good choice.
Pro Tip 3/3Decision Making
Used to emphasize careful thought before making a decision. 
Consider the workload before you commit; do the math first.