Uncertainty is a measurement of risk.

It measures the lack of certainty or sureness of an outcome.

Uncertainty is critical to risk assessment and decision making.

**Formula to calculate uncertainty.**

Before you combine or do anything with your uncertainty, you have to determine the uncertainty in your original measurement.

Uncertainty of a measuring instrument is estimated as plus or minus (±) half the smallest scale division.

**Example:**

Suppose you were measuring a string and found it to be 18.5 cm, calculate its uncertainty.

Since the string is 18.5 cm long, therefore, the smallest scale of division will be 0.05.

Therefore, the uncertainty is ±0.05.