Average Calculator
Paste or type a list of numbers to get the mean, median, mode, range, sum, and count — the full summary at a glance.
The formulas
Median = middle value (or average of the two middle values) when sorted
Mode = most frequent value · Range = max − min
4, 8, 15, 16, 23, 42: sum 108, count 6 → mean 18; sorted middle pair 15 & 16 → median 15.5; range 42 − 4 = 38.
Four employees earn $10, $12, $14, and $16 (in thousands, for a simple illustration): sum = 52, mean = 13. Add a fifth value of $1,000: new sum = 1,052, new mean = 1,052 ÷ 5 = 210.4.
The mean jumped from 13 to 210.4 — nearly 16× higher — because of a single extreme entry. The median of the original four (average of 12 and 14) is 13; with the outlier added, the median only moves to 14, showing why median is the more resistant measure when one value is far from the rest.
Mean vs. median: which to trust
The mean is the everyday "average," but it's easily distorted by outliers — one billionaire in a room makes the mean net worth enormous while the median (middle person) barely moves. That's why economists report median income and home prices. Rule of thumb: use the mean for symmetric data and the median when the data is skewed or has extreme values. The standard deviation calculator tells you how spread out the numbers are around the mean.
Calculating a weighted average
A weighted average multiplies each value by a weight reflecting its importance, adds those products, then divides by the total weight — not by the number of items. Two quiz scores, 70 and 90, average to a simple 80, but if the 90 came from a test worth three times as much (weight 3 vs. weight 1), the weighted average is (70×1 + 90×3) ÷ 4 = 340 ÷ 4 = 85, closer to the more heavily weighted score. See the grade calculator for a ready-made weighted-grade tool.
Common average mistakes
- Dividing a weighted sum by the count of items instead of the total weight. As the quiz example shows, the denominator must be the sum of the weights, not simply how many values you have.
- Reporting the mean of highly skewed data without checking the median. A single extreme value, like the $1,000 outlier above, can move the mean far more than it moves the median.
- Assuming "average" always means the mean. Median and mode are also averages in the statistical sense, and one of them is often the more honest summary for skewed data like income or home prices.
Frequently asked questions
How do I calculate the average?
Sum ÷ count. 4,8,15,16,23,42 → 108 ÷ 6 = 18.
Mean vs. median?
Mean is the arithmetic average; median is the middle value and resists outliers.
What is the mode?
The most frequent value; a set may have one, several, or none.
What is a weighted average, and when do I need one?
A weighted average multiplies each value by its own importance (weight) before averaging — used when items don't count equally, like a final grade where the exam counts more than a quiz. This calculator computes a simple, equally-weighted average; see the grade calculator for a weighted-grade tool.
How do I calculate a weighted average by hand?
Multiply each value by its weight, sum those products, then divide by the total weight. 70 (weight 1) and 90 (weight 3): (70 + 270) ÷ 4 = 85, not the simple average of 80.
How much does one outlier change the mean?
Roughly its distance from the average divided by the count — a big effect in small data sets. Adding a value of 1,000 to 10, 12, 14, 16 moves the mean from 13 to 210.4.
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Last reviewed: September 2026.