Estimation is the approximation of a number, calculation, quantity, or measurement.

Approximation of a Number

The process used to approximate a number is called rounding.

Approximation of a Calculation

A process used to simplify a calculation by rounding the numbers involved in a calculation.

If an approximate answer to the sum 470 + 310 is required, one could round each of the numbers to the nearest hundred to estimate the sum. 470 could be rounded to 500, and 310 could be rounded to 300. The resulting estimate of the sum would be 800, where the actual sum would be 780.

As the rounding becomes greater, the approximation or estimate becomes less precise.

Approximation of a Quantity

An educated guess as to the number of elements in a group.

Estimate how many candies are on the necklace below, then count the candies to see how close your estimate was.


Approximation of a Measurement

A visual approximation the length, area, volume or other measurable attribute of an object.