Portfolio weighted return:
blending each holding by its share

Why a plain average gets the answer wrong

If stocks returned 12% and bonds returned 5%, the plain average is 8.5%. That figure is right only if exactly half of your money sat in each. A portfolio that holds 60% in stocks earned more than that, because the stronger asset carried more rupees.

Weighting each return by its share of the portfolio tells you what the whole pot actually earned. It is the same reasoning that gives a student's final percentage when exams carry different marks.

The weighted-return formula

Weights come from market value at the start of the period, not from what you originally paid. Returns must cover the same time window, so mixing a one-year return with a three-year figure produces nonsense.

A worked example: 60% stocks, 40% bonds

The contributions column is useful by itself. Stocks produced 7.2 of the 9.2 points, so almost four-fifths of the return came from the 60% slice that carried the most risk.

Adding a third holding

A larger portfolio simply adds more terms. Take 50% in equity funds earning 12%, 30% in debt funds earning 6% and 20% in gold earning 8%.

Check that the weights sum to 100% before trusting the result. A sheet where they add to 95% or 105% is a common source of quiet errors.

Drift: the weights do not stay put

After the year in the 60/40 example, stocks have grown faster than bonds, so the mix changes by itself. Starting with ₹100: stocks become 60 × 1.12 = ₹67.20, and bonds become 40 × 1.05 = ₹42.00. The total is ₹109.20, which confirms the 9.2% return.

Rebalancing restores the target mix by selling some of what has risen and buying what has lagged. It controls risk rather than boosting return, and costs such as taxes and exit loads should be weighed against it.

Reading contributions, not just the total

The total tells you the outcome; the contribution of each holding tells you why. In the three-asset case, equity delivered 6.0 of the 9.4 points, which is about 64% of the return from half the money. Debt supplied 1.8 points from 30% of the money, and gold added 1.6 points from the remaining 20%.

That breakdown shows where a bad year would hurt. If equity returned −10% instead of 12%, its contribution would turn into −5.0 points and the portfolio would fall to 1.8 + 1.6 − 5.0 = −1.6%. The holdings that are a large share of the money, and also the most volatile, drive the swings in the total.

Comparing contributions to weights also helps in judging whether a position is paying its way. A holding with 20% of the money that contributes 8% of the return is neither a drag nor a hero, while one that contributes nothing deserves a question about why it is there.

What changes over more than one period

Weighted returns add up cleanly within one period because the weights are fixed at the start. Over several years the weights drift, contributions arrive and money moves, so you cannot add yearly figures or average them and expect the true growth rate.

Chain the periods instead: multiply the growth factors. A portfolio that returned 9.2% in one year and 4% in the next grew by 1.092 × 1.04 = 1.1357, or 13.57% over the two years, not 13.2%. For a portfolio with regular contributions, a money-weighted measure such as the internal rate of return reflects the timing of your cash.

Choosing the return inputs sensibly

The result is only as good as the returns fed in. For a past period, use actual returns that include dividends and interest, after fees, over the same dates. For a forward-looking estimate, use cautious assumptions rather than the best year in memory, because a plan built on 12% from equity can fall short in a decade that delivers 7%.

• Use total return, not just price change, for shares and funds.
• Deduct fund expenses and trading costs so the figure reflects what you keep.
• Use a range of inputs, such as low, middle and high, and look at all three results.

If the three outcomes are far apart, the allocation is doing a lot of the work and deserves more thought than the spreadsheet cell it occupies.

Limits of a single weighted number

• It is a one-period figure. Over several years returns compound, so you cannot add yearly weighted returns and expect the right total.
• It says nothing about risk. A 9.2% blend made of one volatile asset and one steady one behaves very differently from one built differently.
• Cash flows in and out during the period distort the result unless you use a time-weighted method.
• Past returns by asset are not forecasts, so any expected-return assumption should be stress-tested with lower values.

For a quick estimate of a few holdings, a returns tool can sum the pieces. For long periods or contributions, a dedicated time-weighted or money-weighted method is better.