noun / verb
estimate
ES-tuh-mayt/ˈestɪmeɪt/
A rough calculation or judgment, or the act of making one.
She estimates the watermelon's weight by lifting it.

Etymology
The underlying idea is appraising worth. Estimate broadened from judging value to forming an approximate notion, allowing the same act of judgment to concern size or amount as well as worth.
In context
you might need to estimate the amount of data that you're dealing with so you can do some quick calculations for example you can calculate storage size or bandwidth requirements
More examples
- My first estimate was too low.
- They estimated the crowd at three hundred people.
- We need a written estimate before work begins.
Forms
estimate · estimates · estimated · estimating
estimation noun — an approximate calculation or judgment
Similar words
- approximation
- A value close to the actual one.
- assessment
- A broader evaluation that need not be numerical.