Weighted Portfolio Return: Formula and Worked Example

Define a common return period

For holdings measured over the same period with no external cash flows during that period, portfolio return is the sum of each holding's return multiplied by its beginning-value weight. Write this as R=Σwᵢrᵢ, with the weights summing to one. The weights represent invested value, not the number of securities or their share counts. A Weighted Grade Calculator may perform superficially similar arithmetic, but its educational labels do not describe investment performance. Use the explicit portfolio formula here and the ROI Calculator to check the combined beginning and ending values.

Work through a two-holding example

Suppose a portfolio begins with 6,000 in holding A and 4,000 in holding B. Their beginning weights are 60% and 40%. Over the same period, A returns 10% and B returns −5%. The portfolio return is 0.60×10%+0.40×(−5%)=4%. In value terms, A ends at 6,600 and B at 3,800, giving a total of 10,400. The gain of 400 divided by the initial 10,000 also equals 4%. The agreement between the weighted and value-based approaches checks the calculation from two directions.

Use beginning weights for this calculation

The ending weights in the example are 6,600/10,400 and 3,800/10,400, approximately 63.4615% and 36.5385%. Applying these ending weights to the past-period returns gives about 4.5192%, which is not the portfolio's actual 4% return. The better-performing holding has already grown into a larger ending weight. Using that larger weight retrospectively credits it with capital it did not have at the start. Ending weights can be relevant to the next period's exposure, but the simple historical weighted-return formula requires beginning weights for the period being measured.

Include distributions consistently

Decide whether each holding's reported return includes dividends or other distributions. A price-only return for one holding and a total return for another do not form a consistent portfolio comparison. If a portfolio begins at 10,000, ends at 10,300 and pays 100 to the owner during the period, a simple holding-period calculation under this no-other-flow example is (10,300+100−10,000)/10,000=4%. If the 100 distribution is already retained in the ending portfolio value, adding it again would double count it. Record how distributions and fees enter the numbers.

Treat contributions and withdrawals as a separate problem

If new money is added midway through the period, the change in the account balance cannot be interpreted as investment gain without accounting for that flow. A 10,000 account that receives a 5,000 contribution and finishes at 15,000 has not necessarily earned 50%. Time-weighted methods split performance around external cash flows and link subperiod returns. Money-weighted methods consider the amounts and timing of the flows. These are different questions from a beginning-value weighted average of simultaneous holding returns. Choose the method that matches the performance question before combining percentages.

Do not average returns across time as though they were holdings

Two consecutive returns of +10% and −10% produce a cumulative return of 1.10×0.90−1=−1%, even though their arithmetic average is zero. The first year's ending value becomes the second year's starting value, so the periods compound. By contrast, a 50/50 portfolio whose two holdings simultaneously return +10% and −10% has a zero single-period return under the simple no-flow assumptions. The difference is not a contradiction: one example combines periods and the other combines holdings within one period. State which axis the weighting applies to.

Verify the reported percentage and its scope

For the two-holding example, enter initial investment 10,000 and final value 10,400 in the ROI Calculator and expect 4%. This verifies the total-value arithmetic only; the calculator does not import a brokerage history, identify cash flows or reconcile fees. Check that all weights use the same currency and valuation date, and that the return period matches. A result can be mathematically correct while omitting costs or using incomparable definitions. Preserve the component values, return conventions and flow assumptions with the percentage so the performance claim can be reproduced and interpreted accurately.

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