How to use this weighted average calculator
Calculate an average when some values should count more than others. Enter a value and a nonnegative weight on each row. Weights can represent credits, percentages, or quantities; the calculator divides by their actual total, so they do not need to sum to 100.
- Enter the value values in the labeled fields, using consistent units.
- Load the example to inspect the expected format, then replace it with your own values.
- Select Calculate and check the result alongside its working. Reset starts a fresh calculation.
Weighted Average formula
Weighted average = Σ(value × weight) ÷ Σweights
Multiplying every weight by the same positive number leaves the answer unchanged. Weights 4 and 6 have the same relative influence as 40 and 60. A zero-weight row contributes nothing to the result.
Follow the numbers
80 at weight 40 and 90 at weight 60 give (3,200 + 5,400) ÷ 100 = 86.
Load the example above to inspect the entries, then change one value and calculate again. The result follows your selected method. Display rounding changes how the answer is shown; it does not change the underlying observations or weights.
What to check before using the result
Negative weights are not supported. At least one weight must be positive. Percentage weights are normalized by their total rather than forced to 100.
Keep enough precision in the source values for your task. A result calculated from rounded summaries can only be as precise as those summaries. If a number was mistyped or an observation is missing, correct the inputs and calculate again before copying or exporting the answer.
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Common mistakes to avoid
- Confusing a blank with zero. A real zero is an observation. Missing information is not automatically zero.
- Mixing incompatible scales. Use consistent units, or normalize values before combining them.
- Rounding too early. Keep the original values and round at the result stage.
- Using the wrong weighting. Negative weights are not supported. At least one weight must be positive. Percentage weights are normalized by their total rather than forced to 100.
Frequently asked questions
What formula does this calculator use?
Weighted average = Σ(value × weight) ÷ Σweights. 80 at weight 40 and 90 at weight 60 give (3,200 + 5,400) ÷ 100 = 86.
What should I check about the method?
Negative weights are not supported. At least one weight must be positive. Percentage weights are normalized by their total rather than forced to 100.
How many entries can I use?
Paste up to 10,000 values, or use up to 100 individual rows when the chosen input method supports them. Numbers must be finite and no greater than 1 trillion in magnitude. Group and old-count inputs have additional whole-number requirements.
Are the displayed decimals exact?
The calculation uses standard floating-point numbers and compensated addition. Results are rounded only for display. Very small values use scientific notation so they do not silently appear as zero. Select the display precision you need, while respecting the accuracy of your original data.
Are my entries saved or sent anywhere?
The calculator performs its arithmetic in your browser. It does not automatically store entries or send them to a server. Copy, print, and CSV actions happen only when you choose them.
Read our calculation methodology for supported precision, validation, and assumptions.