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Calculate the mean and median of any set of numbers, separated by spaces or commas.
Calculate the mean and median of any set of numbers, separated by spaces or commas.
Enter values above and click Calculate — results will appear here with the formula explained.
The arithmetic mean — the most common meaning of 'average' — adds every value together and divides by how many there are. It uses all the information in the data set but is sensitive to outliers: one extreme number can pull it up or down noticeably. For 12, 18, 7, 25, 9 the sum is 71 across five numbers, so the mean is 14.2.
The median is the middle value once the data is sorted, which makes it robust against outliers. Sorted (7, 9, 12, 18, 25), the middle is 12. When mean and median diverge — say mean 48 but median 12 after adding one 200 — the gap itself diagnoses skew, the classic income-data pattern where a few extremes distort the average.
How to find the average step by step: add all values, count them, divide sum by count. With decimals, keep full precision until the final step — rounding mid-way (14.23 → 14.2 → 14) compounds error across long lists. This calculator rounds only the display to four decimals.
Weighted averages govern grades, portfolios and ratings: multiply each value by its weight, sum, then divide by total weight. A 90 exam at 60% plus 70 homework at 40% is (90×0.6 + 70×0.4) = 82, not the simple mean 80. Simple averages silently assume equal weights — wrong for GPAs, investment returns and review scores.
Outlier handling separates naive from sound averaging: trim extremes (Olympic scoring drops high/low), prefer median for skewed distributions (house prices, salaries), and report both mean and median when they disagree. A single billionaire in a room of teachers makes the mean income meaningless while the median stays honest.
Calculate the mean and median of any set of numbers, separated by spaces or commas. Formula: mean = (sum of all values) ÷ (number of values).
The arithmetic mean — the most common meaning of 'average' — adds every value together and divides by how many there are. It uses all the information in the data set but is sensitive to outliers: one extreme number can pull it up or down noticeably. For 12, 18, 7, 25, 9 the sum is 71 across five numbers, so the mean is 14.2.
The median is the middle value once the data is sorted, which makes it robust against outliers. Sorted (7, 9, 12, 18, 25), the middle is 12. When mean and median diverge — say mean 48 but median 12 after adding one 200 — the gap itself diagnoses skew, the classic income-data pattern where a few extremes distort the average.
How to find the average step by step: add all values, count them, divide sum by count. With decimals, keep full precision until the final step — rounding mid-way (14.23 → 14.2 → 14) compounds error across long lists. This calculator rounds only the display to four decimals.
Weighted averages govern grades, portfolios and ratings: multiply each value by its weight, sum, then divide by total weight. A 90 exam at 60% plus 70 homework at 40% is (90×0.6 + 70×0.4) = 82, not the simple mean 80. Simple averages silently assume equal weights — wrong for GPAs, investment returns and review scores.
Outlier handling separates naive from sound averaging: trim extremes (Olympic scoring drops high/low), prefer median for skewed distributions (house prices, salaries), and report both mean and median when they disagree. A single billionaire in a room of teachers makes the mean income meaningless while the median stays honest.
For 12, 18, 7, 25, 9: the sum is 71 and there are five numbers, so the mean is 71 ÷ 5 = 14.2. Sorted (7, 9, 12, 18, 25), the middle value is 12, which is the median. A weighted case: exam 90 at 60% weight plus homework 70 at 40% gives (54 + 28) = 82 — two points above the naive mean of 80.
Formulas are standard public references (see our methodology). External standards are cited in the text where they apply.
Last reviewed: September 2026 · Report an error