The rounding calculator makes it easy to round numbers by using different rounding formulas. Decide which is the last digit to keep; Leave it the same if the next digit is less than 5 (this is called rounding down); But increase it by 1 if the next digit is 5 or more (this is called rounding up) There are several different methods for rounding.Here we look at the common method, the one used by most people.. First some examples (explanations follow): How to Round Numbers. Following this rule, 2.315 and 2.325 both round to 2.32—instead of 2.325 rounding up to 2.33—when rounded off to the nearest 100th. Common Method. 1.4 Rounding off (EMA8). Rounding off a decimal number to a given number of decimal places is the quickest way to approximate a number. For example, if you wanted to round off \(\text{2,6525272}\) to three decimal places, you would: The rationale for the third rule is that approximately half of the time the number will be rounded up and the other half of the time it will be rounded down. Rounding calculator is the best rounding numbers calculator.