Weighted Average Calculator – Weighted Mean With a Target Score Solver

Some numbers should count more than others. Add your values with the weight each one carries — credits, percentages, quantities — and this calculator finds the weighted mean, shows how it compares with the plain average, and works out the score you still need to hit the target you have in mind.

Where the weight sits — and the score you still need

Each bar is one item’s share of the total weight. The longer the bar, the harder that value pulls the average toward itself. Underneath, the target solver uses the same rows: tell it how much weight is still to come and the average you want, and it finds the value that remaining work has to deliver.

Keep exploring

Averages come in several flavours — these neighbours cover the rest of the family.

How it works in three steps

How the weighted mean is worked out

Going deeper

Percentages, points or credits — do weights have to add to 100?

No. A weight is a share, not a total that has to reach a particular number. The calculation divides the sum of value-times-weight by the sum of the weights, so any set of weights that keeps the same proportions gives the same answer. That is why the anchor example can be written three ways and never moves: weights of 1, 2 and 1, weights of 25, 50 and 25, and weights of 0.25, 0.5 and 0.25 all give 82.5 for the scores 80, 90 and 70.

Weights that add to some other total work the same way. Scores of 80, 90 and 70 with weights of 20, 30 and 40 give products of 1600, 2700 and 2800, a product total of 7100 and a weight total of 90, so the weighted average is 7100 / 90 = 78.89. Nothing needs to be normalised first, because the division by the weight total does the normalising. The rescale button in Advanced options is therefore a display convenience, not a calculation step: it rewrites each weight as its share of 100 at full precision, so the proportions are untouched and the average does not move.

Enter weights exactly as they are given to you. If a syllabus says homework is 20 percent, quizzes 30 percent and exams 50 percent, enter 20, 30 and 50. If a transcript gives credits, enter the credits. If a stock list gives share counts, enter the share counts. Converting between those forms is only worth doing when a report or a form demands one particular form, and converting wrongly is one of the commonest mistakes: turning percentages into decimals and then dividing by 100 a second time turns 82.5 into 0.825, which is not an average of anything.

Dropping the lowest score — what changes and what does not

Many courses drop the lowest quiz or assignment before averaging. In weighted-average terms that means removing one row entirely — its value and its weight both leave the calculation — and then dividing the remaining products by the remaining weight total. Dropping the lowest value can only lift the average, or leave it unchanged when every value is already equal, because the value holding the average down is gone.

On the anchor rows, dropping the 70 (weight 1) leaves the products 80 and 180, a product total of 260 and a weight total of 3, so the average rises from 82.5 to 260 / 3 = 86.67. The drop-lowest preview in Advanced options does exactly this for whatever rows you have entered, and it names the row it dropped so the change is transparent. It is a preview only: the main result at the top of the page keeps all of your rows, because silently changing the headline result would misreport the average you actually entered.

Two cautions matter. First, drop the lowest value, not the lowest weight: a small-weight row with a high score barely moves the average, while a heavy row with a low score drags it hard, and the preview drops by value for that reason. Second, only drop a score when the rules allow it. A course that drops the lowest quiz says so in its syllabus; a course that does not has no dropped row, and reporting the dropped figure as your grade would overstate it. When in doubt, report the all-rows figure and treat the preview as a what-if.

Grade scales: letters, grade points and the 4.0 scale

A weighted GPA is the same calculation with different labels: the values are grade points and the weights are credits. A 4.0 in a 3-credit class and a 3.0 in a 4-credit class give products of 12 and 12, a total of 24 and a credit total of 7, so the GPA is 24 / 7 = 3.43. The simple mean of 4.0 and 3.0 is 3.5, and the weighted figure sits below it because the bigger class carries the lower grade. That gap between the two means is the whole reason weighting exists: equal treatment would pretend a 3-credit class and a 4-credit class mattered the same.

The table above is the common United States 4.0 scale, shown because it is the scale most readers meet first. It is not universal: some schools use plus and minus differently, some do not use them at all, some add bonus points for honours or advanced classes before weighting, and some countries use entirely different scales. The base guide on this page already warns to check your school’s scale, and that warning stands — convert with your own school’s table, not this one, when the two disagree.

To use the table, convert each letter to points, enter the points as values and the credits as weights. An A over 3 credits, a B+ over 3 credits and a B over 4 credits become the rows 4.0 (3), 3.3 (3) and 3.0 (4): products 12, 9.9 and 12, a total of 33.9 over 10 credits, a GPA of 3.39. The preset button in Advanced options loads the simpler two-row example, 4.0 over 3 credits and 3.0 over 4 credits, giving 3.43, so you can see the shape of the calculation before entering your own grades. A semester GPA weights classes by credits; a cumulative GPA is the same formula run over every class, with each class weighted by its credits, which is why a heavy semester moves a cumulative GPA more than a light one.

Bulk entry and paste import — working with a full gradebook

Three rows suit a textbook example, but a real gradebook has dozens of entries, and typing them one at a time invites transcription slips. The paste import in Advanced options takes a whole list at once: write one value and one weight per line, separated by a comma, a space, a semicolon or a tab, then press Load rows. The import replaces the rows above, so a fresh paste always starts clean, and it reports how many lines it skipped, rather than failing the whole paste over one bad line. Up to 200 rows are kept from a single paste. For manual entry, the Add 10 blank rows button adds ten rows at once, and the tool itself has no fixed row limit — the earlier audit item about raising a row cap turned out to have no cap to raise, so bulk entry is the real improvement and it is what was built.

A worked gradebook shows the import format and the arithmetic together. Paste these four lines and the tool returns 89.0:

The product total is 890 and the weight total is 10, so 890 / 10 = 89.0. A line is skipped when it does not contain exactly one value and one weight, when either part is not a number, or when the weight is zero or negative — the same rules the row inputs enforce, with the same reason: a weight of zero or less cannot take part in an average, and the engine says so rather than silently ignoring the row. After loading, check the weight total in the results: if it does not match the total you expected, a line was probably skipped, and the status message under the import box says how many.

Weighted averages beyond school — stock, survey and index examples

Grades are the most familiar use, but any average over items that differ in size is a weighted average waiting to happen. The formula never changes; only the labels on the values and weights do.

Average share price. Buying the same stock at different prices gives an average cost per share weighted by shares, not by purchases. Buying 40 shares at 20, 60 shares at 22 and 100 shares at 18 costs 800, 1320 and 1800, a total of 3920 over 200 shares, so the average cost is 3920 / 200 = 19.60 per share. Averaging the three prices plainly would give 20, which overstates the cost because the cheapest purchase was also the largest. Note the scope honestly: this tool weights price by shares only, so fees or commissions are not part of its calculation — add any fees to the cost total yourself before dividing if your broker charges them.

Survey scores. Two groups rating the same thing should not count equally when one group is larger. A group of 120 people scoring 7.2 and a group of 80 scoring 8.1 give (7.2 × 120) + (8.1 × 80) = 864 + 648 = 1512 over 200 people, a weighted score of 7.56. The simple mean of 7.2 and 8.1 is 7.65, which over-weights the smaller group. Whenever a published average comes from groups of different sizes, the honest figure is the size-weighted one, and the gap between the two is a quick check on whether a headline number was computed carefully.

Average cost in stock. A shop holding the same item bought at different prices values its stock at the quantity-weighted average cost, by the same arithmetic as the share example: each purchase price weighted by how many units were bought. The pattern to recognise is always the same — a per-unit figure (price, score, grade) paired with a count of units (shares, people, credits, items). When every unit counts once, the plain mean is enough; when units arrive in batches of different sizes, weighting by batch size is what keeps the average honest.

Mistakes that quietly move a weighted average

Weighted-average errors rarely announce themselves, because the calculation still produces a plausible-looking number. Five mistakes cover most of them.

Dividing by the count instead of the weight total. With weights of 25, 50 and 25, the product total is 8250. Dividing by 3, the number of rows, gives 2750 — a number on no scale the inputs used. The divisor is always the weight total, here 100, giving 82.5. Whenever a result looks wildly out of range, check the divisor first.

Converting percentages twice. Weights of 25, 50 and 25 as decimals are 0.25, 0.5 and 0.25, whose total is 1, so the product total of 82.5 divided by 1 is 82.5. Dividing by 100 again gives 0.825. Pick one form — percentages or decimals — and divide by that form’s weight total, not by both.

Forgetting a row in the denominator. Every weight in the numerator must also appear in the denominator. Leaving the heaviest row out of the weight total inflates the result, and leaving it out of the numerator deflates it; the results box on this page shows the weight total it used, so comparing that total with your own addition catches the slip.

Using a zero or negative weight. A weight of zero says an item should count for nothing, which is the same as removing the row, and a negative weight would pull the average away from the item. The tool rejects both with a plain message rather than guessing, so an empty weight box or a mistyped minus sign stops the calculation visibly instead of corrupting it quietly.

Mixing scales in one list. Percent scores and grade points cannot share a list: 90 (a percent) and 3.0 (a grade point) averaged together describe nothing. Convert every value to one scale first — the grade-scale table in the section above is the conversion for letters — and only then weight them.

Reading the target solver — ‘Not reachable’ and ‘Already there’

The solver under the weight bars answers a backwards question: given the rows already banked, what must the remaining work score to reach a target? It works from the finished total. With 330 banked over a weight of 4, a remaining weight of 2 and a target of 85, the finished total must be 85 × 6 = 510, so the remaining work must supply 510 − 330 = 180 over a weight of 2, a score of 90. That is the normal case, and the solver states it plainly.

Two honest edge cases deserve their own readings. A target of 95 with the same banked rows needs (95 × 6 − 330) / 2 = 120, above the top score of 100, so the solver reports Not reachable and adds the best possible outcome: even a perfect 100 on the remaining weight gives (330 + 200) / 6 = 88.33, short of 95. That is not a failure of the tool; it is the arithmetic telling you the target needs more banked weight, a different target, or both. The other edge is a target of 50, which needs (50 × 6 − 330) / 2 = −15, a negative score, so the solver reports Already there: even a zero on the remaining weight leaves 330 / 6 = 55, above the target. A target of 70 sits between the edges and needs (70 × 6 − 330) / 2 = 45, an ordinary reachable score.

Remember what the solver counts as done: every row above is treated as finished, and the remaining weight is whatever is still to come — a final exam, the rest of a course, the stock not yet bought. If a row is not finished yet, remove it from the rows and put its weight in the remaining-weight box instead, or the solver will treat unfinished work as banked and understate the score you need.

New guide: Weighted Averages Explained: Weights, Moving Averages, and Grades

An ordinary average treats every value equally.

Weighted mean = the sum of (value × weight) divided by the sum of the weights. Forgetting the division — or dividing by the number of values instead of the total weight — is the commonest error, and it always overstates or understates the answer. The full guide, Weighted Averages Explained: Weights, Moving Averages, and Grades, works through the method in detail, with worked examples and the cases that most often go wrong.

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