Average Calculator
Calculate the mean, median, mode, and sum of a set of numbers.
Mean, Median, Mode — When to Use Which
The mean uses every value but is dragged by outliers: one $5M house among ten $300k homes pushes the mean above every actual home price. The median resists outliers because it only ranks values — that is why home prices and salaries are reported as medians.
Mode is the only average that works on non-numeric data (most common color, most common size). A distribution can have no mode or several; when mean ≈ median ≈ mode, the data is roughly symmetric.
Worked Example: Weekly Sales 12, 15, 15, 18, 40
Mean = (12+15+15+18+40) ÷ 5 = 100 ÷ 5 = 20
Median = middle of {12,15,15,18,40} = 15
Mode = 15 (appears twice)
The mean (20) sits above 4 of the 5 values — the 40 outlier pulls it up
Report the median (15) when the data is skewed: 'a typical week was 15 sales'. The mean answers 'total ÷ periods' questions; the median answers 'what is typical'.
Frequently Asked Questions
When should I use median instead of mean?
Whenever the data is skewed or has outliers: incomes, house prices, response times, hospital stays. A rule of thumb: if mean − median > 10% of the mean, the distribution is skewed and the median tells the truer story.
What is a weighted average?
Each value contributes proportionally to its weight: Σ(wx)/Σw. Course grades are the classic case (exams weighted more than quizzes). The simple mean is the special case where all weights equal 1.
Can mean, median and mode all be different?
Yes — in skewed data all three separate. Right-skewed data (most income distributions): mode < median < mean. In a perfectly normal distribution, all three coincide at the same value.
How many decimal places should I report?
Match the precision of your input data. If measurements are whole numbers, one decimal on the mean is plenty. Extra digits imply accuracy the data doesn't have.
Authoritative Sources & Further Reading
Last reviewed: September 2026. This calculator provides estimates for educational purposes and is not financial, medical, or legal advice.
Common Mistakes & Pro Tips
Avoid these mistakes
Averaging percentages of different bases
If half your students score 60% on a 100-point test and half score 80% on a 200-point test, the average score is NOT 70%. Convert to the same basis first (points or weighted score), then average — mixing bases silently overweights one group.
Averaging rates over unequal periods
A fund returning 10% in year 1 and −10% in year 2 averages 0%, but $1,000 becomes $990 — a real loss of 1%. Sequential percentage changes compound; only equal-weighted returns over identical periods can be averaged directly.
Hiding outliers in small samples
With fewer than about 10 values, a single extreme dominates the mean: nine salaries of $50k and one of $500k average $95k — a figure no one in the group earns. Report the median alongside the mean whenever the sample is small or skewed.
Pro tips
Mean vs median vs mode
Mean uses every value but is dragged by outliers; median is the 50th-percentile point and ignores magnitude; mode finds the most frequent value and works on non-numeric data. Income and house-price statistics report medians precisely because distributions are right-skewed.
Weighted averages in one line
When values carry weights (credits, quantities, hours), multiply each value by its weight, sum, then divide by the total weight: Σ(wᵢxᵢ)/Σwᵢ. A GPA is exactly this — grade points weighted by credit hours.
Moving averages smooth time series
A 7-day moving average of daily cases, sales or temperatures filters weekday/weekend noise. Each point is the mean of the previous 7 days; longer windows smooth more but react later to genuine shifts.
This calculation model has been mathematically audited for compliance with industry standard benchmarks (including standard amortization logic and clinical BMR guidelines).
Need help?
Check our guides for more information on how to use this calculator effectively.
Read our guides