Exact number

Definition

An exact number is a value that is known with complete certainty, often through counting or defined quantities. Exact numbers have an infinite number of significant figures and do not contribute to measurement uncertainty.

5 Must Know Facts For Your Next Test

1. Exact numbers are not subject to measurement error or uncertainty.
2. Common examples include counted items (e.g., 3 apples) and defined constants (e.g., 1 kilogram = 1000 grams).
3. Exact numbers can have an infinite number of significant figures.
4. They play a crucial role in calculations as they do not affect the precision of the result.
5. When performing calculations, exact numbers do not limit the number of significant figures in the final answer.

Related terms

Measured Number: A value obtained through measurement, which inherently includes some level of uncertainty and thus has limited significant figures.

Significant Figures:

Digits in a measured or calculated quantity that contribute to its precision, including all certain digits and one uncertain digit.

Uncertainty:

The range within which the true value of a measured quantity is expected to lie; reflects limitations in measurement precision.