Estimation is making a rough calculation of value, number, or quantity. Students' Estimation skills develop quite slowly in the early school years but are still an indicator of their abilities to represent and manipulate numbers, crucial skills for arithmetic proficiency.

There are four main types of Estimation:

Computational Estimation is providing an approximate answer to an arithmetic problem without exact calculation. This is usually used for addition and subtraction problems with large (two to three digit) numbers.

Measurement Estimation is drawing or guessing line lengths.

Number line Estimation is approximately positioning where a number or set of numbers belongs on a number line.

Numerosity Estimation is approximating the number of objects.