Average Calculator
Enter up to five numbers to find their arithmetic average (mean). The calculator sums all values and divides by five. Enter 0 for any fields you don't need — the content below explains how to interpret results when using fewer than five values.
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Formula
Mean = (x₁ + x₂ + … + xₙ) / n
The arithmetic mean is the sum of all values divided by the count of values. This calculator uses five slots; if you only have three numbers, enter 0 in the remaining fields and mentally note that the divisor is 5 (not 3), so the displayed mean will be lower than a true three-number average. For a three-number average, sum your three values and divide by 3 manually, or use a dedicated calculator that tracks non-zero count.
How to use the Average Calculator
- 1
Enter your number 1
- 2
Enter your number 2
- 3
Enter your number 3
- 4
Enter your number 4
- 5
Enter your number 5
- 6
Read your results instantly
Results update in real time as you type.
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Arithmetic mean vs. other types of average
The word 'average' usually means arithmetic mean, but there are several types of average, each suited to different situations.
The arithmetic mean — sum divided by count — is appropriate when values are additive and similarly scaled, like exam scores or temperatures.
The geometric mean — nth root of the product — is better for rates and ratios, like compound annual growth rates. If a portfolio grows 10%, then 20%, then −5%, the arithmetic mean return is 8.33%, but the geometric mean is the true average per-period return: about 7.8%.
The harmonic mean — n divided by the sum of reciprocals — applies when you're averaging rates of the form 'x per unit,' such as speeds over equal distances.
Always ask which mean is appropriate before computing.
When the average is misleading
The arithmetic mean is sensitive to outliers. In a group of five salaries — $40k, $42k, $45k, $48k, $1M — the mean is about $235k, which describes no one in the group. The median ($45k) is far more representative.
Skewed distributions are common: household income, city populations, website traffic, net worth, and many biological measurements are right-skewed with a long tail of large values. In these cases, reporting only the mean gives a distorted picture.
For a complete summary, report the mean alongside the median and a measure of spread (range or standard deviation). Together they tell you both the center and how much individual values vary.
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Weighted averages
A simple average treats every value equally. A weighted average assigns different importance to each value. Your GPA is a weighted average: a 4-credit course counts more than a 1-credit seminar.
The weighted mean formula is: (w₁x₁ + w₂x₂ + … + wₙxₙ) / (w₁ + w₂ + … + wₙ). If you scored 80% on a quiz worth 20% and 90% on an exam worth 80%, your weighted average is (0.2×80 + 0.8×90) / 1 = 88%.
Whenever data points don't contribute equally — because of different sample sizes, time periods, or importance — use a weighted average rather than a simple mean.
Tips & Insights
Use 0 for missing values, then adjust
This calculator always divides by 5. If you only have three numbers, enter them in fields 1–3, leave 4 and 5 as 0, then multiply the displayed average by 5 and divide by 3. Alternatively, just divide the shown sum by your actual count of values.
The mean minimizes squared deviations
The arithmetic mean is the value that minimizes the sum of squared differences from itself. This is why it's used in least-squares regression and variance calculations. If you want to minimize absolute (not squared) deviations, use the median instead.
Running average trick
To update an average as new data arrives without recalculating from scratch: new_mean = old_mean + (new_value − old_mean) / new_count. This is numerically stable and efficient for large datasets or streaming data.
Worked Examples
Test score average
Sum = 417. Average = 83.4. The student's mean score across five tests is 83.4, a B-range performance.
Weekly temperature average
Sum = 334°F. Average = 66.8°F. The week's mean high temperature was about 67°F — mild spring weather.
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Frequently Asked Questions
What is the difference between mean, median, and mode?
The mean is the sum divided by count. The median is the middle value when sorted. The mode is the value that appears most often. For symmetric distributions they're all similar; for skewed data they can differ substantially.
How do I average percentages?
Be careful — averaging percentages directly is only valid when each percentage applies to the same base. If 50% of 100 people and 50% of 200 people passed a test, the true overall rate is 150/300 = 50%, which happens to match. But 40% of 50 and 60% of 200 gives 140/250 = 56%, not 50%. Use a weighted average when bases differ.
Can the average be a number not in the dataset?
Yes — and this is common. The average of {1, 2, 3, 4, 5} is 3 (which is in the set), but the average of {1, 2} is 1.5 (which is not). The mean is a mathematical summary, not a required member of the dataset.
How do outliers affect the average?
Outliers pull the mean toward them. A single extreme value can dominate the average of a small dataset. Use the median when outliers are present or when you want a measure that reflects the 'typical' value rather than the mathematical center.
What is a moving average?
A moving average calculates the mean of the most recent n values as new data arrives. It smooths fluctuations in time-series data, making underlying trends easier to see. Commonly used in finance (stock prices), meteorology, and signal processing.
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