Enter a list or weighted rows
For a Simple average, paste a column of numbers or separate numbers with commas. Use a decimal point and no thousands separators: 1,234 is two values, 1 and 234. A zero is a value and counts toward the mean. Negative values are accepted. A bad or missing item produces an error rather than being silently dropped.
For a Weighted average, enter a value and a weight in every row. Use Add row or Remove row to change the list. Weights must be nonnegative and at least one must be positive. They do not have to sum to 1 or 100. Keep the same scale throughout: use either 1 and 3, or 0.25 and 0.75; mixing those scales changes the calculation.
Try example fills the selected mode without calculating. Calculate displays the mean, accepted count and sum. Weighted results also show the sum of weights and sum of products. Reset clears the inputs and restores Simple average. Changing modes clears values and the result. Editing clears the previous answer and copy action.
Method and examples
The arithmetic mean is sum(x) / n, where n is the number of accepted values. For 0, 10, 20, the sum is 30, the count is 3, and the mean is 10.
The weighted average is sum(value × weight) / sum(weight). For 80 with weight 1 and 90 with weight 3, the products total 80 × 1 + 90 × 3 = 350. The weights total 4, so the average is 87.5. Weights 25 and 75 give 8,750 / 100 = 87.5; multiplying every weight by the same positive factor leaves the result unchanged.
A value with weight zero still counts as an accepted row and appears in the ordinary sum of values, but contributes zero to the weighted mean.
Limits and rounding
Enter 1–200 values or rows. Values can range from −1,000,000,000,000 to 1,000,000,000,000 with at most six decimal places. Weights have the same upper bound and precision, with a minimum of zero. Scientific notation is not accepted. Enter every value and weight; blank rows are errors.
The mean is displayed to at most 12 decimal places and marked when rounded. Sum, weight sum and product sum are retained without display rounding. The calculation uses decimal arithmetic; displayed rounded means are never reused as inputs.
This tool calculates a mean. It does not calculate median, mode, GPA, stock cost basis, sporting averages or average rate of change. For relative changes, use the Percentage Change Calculator; for two-part comparisons, use the Ratio Calculator. The Percentage Calculator finds a percentage of a number.