Weighted Average Calculator - Grades & Portfolio

Data Set

Calculate weighted averages for grades, portfolio returns, surveys, and any list of values with weights. Enter rows, use templates, or paste CSV/TSV data.

Select mode

Add rows

Review output

Compare scenarios

This weights exactly the values and weights you entered. Leave an item out, or use the wrong weight basis such as percentage instead of raw count, and the average will be wrong in a way the calculator cannot detect, so double-check your inputs before relying on the result.

Formulas and sources

Each formula this calculator uses, where it comes from, and what it leaves out. "How it works" shows the same formula with your own numbers.

Weighted mean

Every mode

Weighted Mean = Σ(Value × Weight) ÷ Σ(Weight)
Weighted Mean
the result
Value
an item's value or score; negatives are allowed
Weight
how much that item counts, above zero

The weights need not total 100: 3 and 1 give the same mean as 75 and 25. A row with a blank or zero weight is left out, which changes nothing, and so is a value or weight past 1,000,000,000,000.

Source: Uses the formula in NIST's DATAPLOT Reference Manual, "WEIGHTED MEAN" [1]. Its example inputs, values 2, 3, 5, 7, 11, 13, 17, 19 and 23 at weights 1, 1, 0, 0, 4, 1, 2, 1 and 0, give 11.5 here; the manual prints no result.

Weight share and contribution

Every mode

Share = Weight ÷ Total Weight × 100 Contribution = (Value × Weight) ÷ Total Weight
Share
the item's share of the total weight, in percent
Contribution
the part of the mean that comes from that item
Value
the item's value
Weight
the item's weight
Total Weight
the weights of every counted row, added

The contributions add up to the weighted mean. A row's share of the mean, its contribution ÷ the mean, is shown only when every value has the same sign: with mixed signs or a mean of 0, that share has no meaning.

Source: Standard formula; no single publisher. Each contribution is one term of the sum in [1], divided by the total weight.

Sources

  1. National Institute of Standards and Technology (NIST). WEIGHTED MEAN, DATAPLOT Reference Manual, Statistics LET Subcommands, page 2-65, EQ 2-20. March 18, 1997.

What this calculator does not cover

  • It averages the values and weights you enter. It does not choose or estimate the weights, compound returns over several periods, or apply grade-replacement rules.
  • For course grades with a target-GPA planner, see the GPA Calculator.
  • Bulk Paste reads one value and weight per line. A line that does not read as exactly two numbers, or reads two ways, is skipped and counted, never guessed.

Sources checked on .

Help

Quick Start Guide

  1. Select mode: Use Simple, Templates, or Bulk Paste mode.
  2. Add rows: Enter Value and Weight for each row.
  3. Review output: See weighted mean and contribution breakdown.
  4. Compare scenarios: Adjust weights to understand sensitivity.
  5. Export result: Save outputs for reporting or review.

Frequently Asked Questions

The calculator works it out and shows it per row, so you do not have to normalize anything by hand. Weights of 3 and 1 become 75% and 25%; weights of 40,000 and 10,000 become 80% and 20%. It also reports what each row contributes to the final mean in absolute terms. With 85 at weight 3 and 92 at weight 1 the mean is 86.75, of which 63.75 comes from the first row. Weights never need to add up to 100 for this to work.

Last updated