Jason FinanceDollar-cost averaging calculator
Enter your regular investing plan and see how much it would have grown if you had followed it in any period of the last 98 years in the US market (S&P 500, dividends reinvested). Results update as you type.
Historical scenarios: actual S&P 500 returns
Fixed-return scenarios
This tool only calculates from historical data and your assumptions. Past performance does not predict future returns, and nothing here is investment advice.
Data and methodology
Data source
- S&P 500 annual total returns with dividends reinvested, covering 1928 to 2025 โ 98 years.
- The source is the public historical returns dataset by Professor Aswath Damodaran of NYU Stern (Historical Returns on Stocks, Bonds and Bills), widely used in research and financial media.
- The latest year (2025) returned 17.78%; the annualized return for 1928โ2025 is about 10.0%. The dataset is updated once a year, and this tool will be updated after each release.
- Expand the table below to see every yearโs return.
Data source: Aswath Damodaran (NYU Stern), Historical Returns on Stocks, Bonds and Bills
Show S&P 500 annual total returns (1928โ2025)
How the three historical scenarios work
- Say you choose 20 years: your plan is run through 1928โ1947, 1929โ1948 and so on up to 2006โ2025 โ every consecutive 20-year period, 79 in total โ using actual annual returns.
- The periods are ranked by final value: the lowest is the worst case, the middle one is the median and the highest is the best case, each labelled with its years.
- This captures sequence risk: with the same average return, a crash early or late in the plan changes the result a lot. Fixed returns cannot show that, so both are provided.
Calculation
- Contributions are made at the start of each period: the start of each month for monthly plans, the start of each year for yearly plans.
- For monthly contributions, each yearโs return is spread evenly over 12 months: monthly growth = (1 + annual return)^(1/12) โ 1.
- The expense ratio you enter is deducted from each yearโs return; for example, a 10% year with a 0.03% expense ratio counts as 9.97%.
- Annualized return (IRR) accounts for when each contribution was made, so it reflects the yearly return better than final value รท total invested.
What is not included
- Taxes, such as the 30% US withholding tax on dividends for Taiwan residents, which lowers real returns below the index total return.
- Trading costs and transfer fees, such as broker commissions and cross-border wire fees.
- Currency: with TWD selected the exchange rate is assumed constant; in reality TWD/USD moves can improve or worsen the result.
- Inflation: amounts are nominal, so 1 million in 20 years will buy less than 1 million today.
- Small tracking differences between real index ETFs and the S&P 500 index.
FAQ
How is the historical worst case calculated?
Your plan is run through every consecutive N-year period from 1928 to 2025 (N is the number of years you enter) using actual S&P 500 returns. The period with the lowest final value is the worst case, the highest is the best case, and the one in the middle is the median.
Why show fixed returns as well?
Fixed returns such as 4%, 8% and 12% make it easy to compare assumptions, but real returns vary every year and the timing of crashes changes the outcome, so historical scenarios are closer to what investors actually experience.
Can I use New Taiwan dollars?
Yes. With TWD selected, amounts are shown in TWD, but returns are still in US dollars with a constant exchange rate. Investing in US stocks through an overseas broker involves currency moves that will change the result.
How much do fees matter?
The expense ratio is deducted from returns every year. Try changing it from 0.03% to 1% โ over the long run the difference is large.