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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →For a single lump-sum investment held for 15 years, calculate cumulative return as (ending value − beginning value) ÷ beginning value. Multiply by 100 to express it as a percentage. To express those same endpoints as an equivalent annual compound rate, calculate (ending value ÷ beginning value)1/15 − 1. The first number is the gain or loss over the full period; the second is an annualized rate, not the return earned in every individual year.
Calculate the 15-year return from the starting and ending values
Use the amount invested at the beginning and the investment’s value at the end of the 15-year period. Keep the dates and currency consistent. For example, compare the value on a particular date with the value on the same calendar date 15 years later, rather than combining mismatched periods.
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- Record the beginning value. For a single initial investment, this is the amount invested at the start.
- Record the ending value. Use a value for the end date that reflects the dividend treatment you intend to report.
- Subtract the beginning value from the ending value.
- Divide that difference by the beginning value. The result is cumulative return as a decimal.
- Multiply by 100 to state cumulative return as a percentage.
In symbols, let B be the beginning value and E the ending value:
Cumulative return = (E − B) ÷ B
If the result is positive, the ending value is greater than the beginning value; if negative, it is lower. The formula reports the change relative to the original amount, not the ending value as a percentage of the original amount.
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Worked example: $10,000 becomes $30,000
This is hypothetical arithmetic, not a historical stock result. The change is $30,000 − $10,000 = $20,000. Divide $20,000 by $10,000 to get 2; multiply by 100 to get a 200% cumulative return over the full 15 years. The ending value is 300% of the initial investment, while the gain is 200% of it.
Calculate the 15-year compound annual growth rate
Cumulative return answers how much the investment changed across all 15 years. Compound annual growth rate, or CAGR, expresses the beginning and ending values as the constant annual compounding rate that would connect them over that period:
CAGR = (E ÷ B)1/15 − 1
For the hypothetical $10,000-to-$30,000 example, the calculation is (30,000 ÷ 10,000)1/15 − 1, or approximately 7.60% per year. This is a smoothed equivalent rate. It does not mean the investment actually gained 7.60% in each calendar year; the formula uses only the two endpoint values and the 15-year period.
Multiply the decimal CAGR by 100 to report it as a percentage per year. Use 15 as the exponent’s denominator only when the start and end values span exactly 15 years. For a different holding period, use the actual number of years in the exponent’s denominator.
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Which figure should you report?
| Measure | Formula | What it tells you |
|---|---|---|
| Cumulative return | (E − B) ÷ B | The total percentage gain or loss over the entire 15-year period. |
| 15-year CAGR | (E ÷ B)1/15 − 1 | The constant annual compounded rate equivalent to the same beginning and ending values over 15 years. |
Label the result so readers can tell which measure you mean. A statement such as “200% total cumulative return over 15 years” is not interchangeable with “7.60% CAGR per year” in the example: they describe the same endpoints from different perspectives.
Decide how to treat dividends
A stock investment’s share-price change does not by itself account for dividend income. If you want a total-return result that assumes dividends were reinvested, use an ending value or return series that includes those reinvested dividends. Do not add the dividends a second time if the chosen ending value or total-return series already includes them.
S&P Dow Jones Indices explains the distinction in its “Methodology Matters” material: “In a total return index, on the other hand, the changing value is determined by a combination of the price changes and reinvested income from dividends or other cash payouts.” A price-return index reflects price changes without regular dividends; a total-return index includes reinvested dividend income under its stated convention.
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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minute| Return convention | What it includes | Use it when |
|---|---|---|
| Price return | Price changes; regular dividends are excluded. | You want to describe price movement alone or compare against a price-return benchmark. |
| Total return | Price changes plus dividend income reinvested under the series’ convention. | You want a return measure that includes reinvested dividend income. |
For the S&P 500, the headline index commonly cited in media is a price-return index. S&P Dow Jones Indices also publishes an S&P 500 Total Return series that models constituent dividends reinvested on their ex-dividend dates. Those are different series, so name which one you use. The index’s dividend and compounding assumptions are benchmark conventions; they are not a calculation of an individual investor’s precise tax result.
Use consistent dates and return conventions for a benchmark comparison
To compare a stock’s 15-year return with an index, align the measurement dates, currency, and dividend treatment. Comparing a stock result that includes reinvested dividends with a price-return index that excludes them does not put both results on the same basis. Choose either price return for both or a dividend-inclusive total-return convention for both, where suitable data are available.
- Use the same start and end dates for the stock and benchmark.
- Express both values in the same currency, or account explicitly for currency conversion.
- State whether each result excludes dividends or includes reinvested dividends.
- Identify the index series by its return convention rather than referring only to “the S&P 500.”
S&P Dow Jones Indices’ methodology compounds daily return factors and dividend income for its total-return index series. That convention helps define what the benchmark represents, but it does not establish what a particular investor received after personal costs or taxes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Check what the return does not account for
The endpoint formulas describe the relationship between the selected beginning and ending values. They do not automatically adjust the result for expenses, trading costs, personal taxes, or inflation. State whether those items are included or excluded; do not label an unadjusted nominal result as a real or after-tax return.
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- Fund expenses and trading costs: include them only if the values or return series you use already reflect them, or if you separately calculate their effect.
- Taxes: personal tax treatment depends on the investor and applicable jurisdiction. The nominal endpoint formula does not calculate an after-tax result.
- Inflation: a nominal return does not show the change in purchasing power. The formula alone does not produce an inflation-adjusted return.
When these adjustments have not been calculated, describe the result as nominal and state its dividend convention. Avoid implying that it is the investor’s take-home or inflation-adjusted gain.
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When the simple formula is not enough
The beginning-to-ending calculation fits a single initial lump sum with no deposits or withdrawals during the 15-year holding period. If money was added or removed along the way, the ending value reflects both investment performance and the timing and size of those cash flows. One endpoint CAGR does not separate those effects or show the investor’s personal cash-flow experience.
For an account with interim deposits or withdrawals, keep the dates and amounts of those cash flows and use a return method designed to account for them. Do not present the simple endpoint result as though it isolates the investment’s performance for that investor. The figures and formulas here do not specify the detailed calculation for a cash-flow-aware method.
Calculate it with a spreadsheet or calculator
A standard calculator is enough. For beginning value in cell A1 and ending value in cell B1, a spreadsheet can calculate cumulative return with =(B1-A1)/A1 and CAGR over 15 years with =(B1/A1)^(1/15)-1. Format the result as a percentage, or multiply the formula by 100 if you want a numeric percentage rather than percentage formatting.
Texas Instruments documents a CAGR procedure for its BA II Plus and BA II Plus Professional financial calculators using beginning value, ending value, and years; the BA II Plus also has time-value-of-money and percentage functions. A dedicated financial calculator is optional, not a requirement for these two-endpoint calculations.
What to include when you publish or share the result
A useful return statement makes its scope clear enough that someone else can interpret or reproduce it. Include the beginning and ending dates, beginning and ending values, currency, measure, dividend convention, and whether costs, taxes, or inflation are reflected. If comparing with an index, identify the exact price-return or total-return series and use matching dates and currency.
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