Question 1

How do I calculate the average of numbers?

Accepted Answer

Add all the numbers together and divide by how many numbers there are. For example, the average of 10, 20, 30, 40 is (10 + 20 + 30 + 40) / 4 = 25. This is the arithmetic mean, the most common type of average. The calculator above computes this instantly along with median, mode, and other statistics.

Question 2

What is the difference between mean, median, and mode?

Accepted Answer

Mean is the sum divided by count (sensitive to outliers). Median is the middle value when sorted (resistant to outliers). Mode is the most frequent value (useful for categorical data). For the set {2, 3, 3, 5, 100}: mean = 22.6, median = 3, mode = 3. The median and mode are more representative here because the outlier (100) pulls the mean up. Use median for income data, mode for survey responses, and mean for normally distributed data.

Question 3

When should I use median instead of mean?

Accepted Answer

Use median when your data has outliers or is skewed. Classic examples: household income (a few very high incomes skew the mean upward), house prices (a few luxury properties distort the mean), and response times (occasional very slow responses inflate the mean). The median gives a better sense of the "typical" value. Mean is better for symmetric, normally distributed data like test scores or heights.

Question 4

What if there is no mode in my data?

Accepted Answer

If every value appears exactly once (all values are unique), there is no mode — the data has no most frequently occurring value. This is common in continuous data sets with many decimal places. The calculator will display "No mode" in this case. A dataset can also be bimodal (two modes) or multimodal (multiple modes) if several values share the highest frequency.

Question 5

How do I calculate a weighted average?

Accepted Answer

A weighted average multiplies each value by its weight, sums the products, and divides by the total weight. Formula: Weighted Average = Sum(value x weight) / Sum(weights). For example, if homework (weight 30%) = 85 and exams (weight 70%) = 92, weighted average = (85 x 0.30 + 92 x 0.70) / 1.0 = 89.9. Use the GPA calculator on CalcDom for credit-weighted grade averages.

Question 6

What is the range and why does it matter?

Accepted Answer

Range = Maximum value - Minimum value. It measures the spread of your data. A small range means values are clustered together; a large range means they are spread out. For example, test scores of {70, 75, 80, 85} have a range of 15 (consistent performance), while {30, 50, 80, 100} have a range of 70 (high variability). Range is simple but sensitive to outliers — a single extreme value can make the range misleading.

Question 7

How do I calculate the average of percentages?

Accepted Answer

You can only average percentages directly if they all represent the same base quantity. If the bases differ, you must calculate a weighted average. For example, if Store A has 80% satisfaction (100 customers) and Store B has 90% satisfaction (300 customers), the correct overall average is (80 x 100 + 90 x 300) / (100 + 300) = 87.5%, not 85%. Simply averaging 80% and 90% gives an incorrect result when the sample sizes differ.

Average Calculator — Mean, Median, Mode & More