The approximate value of something is an estimate.
An estimate is an educated guess. Approximate and round off mean "about".
Approximate
If an estimation, or estimate, is a guess, an approximate estimation is a rougher guess.
Estimate
about, guess
It is an estimate
Estimates are never exact. They are a best guess at what the answer is. They are always going to be approximate.
The 2010 estimate is 1,180,166,000
Make a very approximate estimate.
It's pretty much like an estimate.
approximate caculation