Average Calculator

Mean is the arithmetic average (sum divided by count). Median is the middle value when sorted. Mode is the most frequent value. For symmetric distributions, all three are similar. For skewed data (like income), the median is often more representative than the mean.

Use median when data is skewed or has outliers. For example, average household income is misleading because billionaires pull it up — median income better represents the typical household. Mean works best for symmetric data without extreme outliers.

Standard deviation measures how spread out data is from the mean. Low std dev means values cluster near the mean; high std dev means they spread widely. About 68% of data falls within 1 standard deviation, 95% within 2.

Multiply each value by its weight, sum the results, and divide by the total weight. Example: if a final exam is worth 40% and midterm 60%, and you scored 80 and 70: weighted avg = (80×0.4 + 70×0.6) = 32 + 42 = 74.

Population std dev divides by N (total count); sample std dev divides by N-1 (Bessel's correction). When your data is a sample from a larger population (most real-world cases), use sample std dev. Our calculator uses population std dev.