How much does it matter when you start saving for retirement? Points Frog's retirement calculator answers with compound growth in today's dollars, and the gap is large. Saving $500 a month from age 25 grows to about $580,532 by 65 at a steady 4% a year after inflation. The same $500 a month started at 45 reaches about $181,921.
The early saver puts in twice as much money, $240,000 against $120,000, but ends with about 3.2 times as much. In the calculator's optimistic case, which uses the S&P 500's 6.8% average after inflation since 1957, the gap is wider still: $1,172,810 against $248,079, more than four times as much. That gap is compounding. Returns earn their own returns for longer.
A worked example
The calculator opens on a 35-year-old who has $50,000 saved, adds $750 a month and wants $40,000 a year from savings when they retire at 65. A common target is 25 times that yearly income, so the goal is $1,000,000.
At a steady 4%, the savings reach $676,123 by 65, about 67% of the goal. That balance would pay about $27,045 a year at a 4% withdrawal rate. At the optimistic 6.8%, the savings reach $1,205,257, past the goal, and would pay about $48,210 a year.
| Case | Balance at 65 | Pays about, a year |
|---|---|---|
| Steady (4%) | $676,123 | $27,045 |
| Optimistic (6.8%) | $1,205,257 | $48,210 |
| Goal | $1,000,000 | $40,000 |
So the verdict is "on track only if markets match S&P 500 history." The calculator then gives the monthly saving that removes the need for strong markets: $1,223 a month, against $750 now.
What moves the answer most
Starting age matters most. At 6.8% after inflation, money doubles about every 11 years. That is why $10,000 invested at 25 grows to about $138,947 in today's dollars by 65, while the same $10,000 invested at 45 grows to about $37,276.
The income you want sets the goal. Under the 25-times rule, each $10,000 a year of income from savings adds $250,000 to the target. Wanting $60,000 a year means a $1,500,000 goal, and $100,000 a year means $2,500,000. The calculator asks for income after Social Security or a pension, so only the part your savings must cover counts.
Monthly saving and retirement age are the other levers. In the example above, working two more years, to 67, lifts the steady balance to about $749,989. It also cuts the monthly saving needed to reach the goal to about $1,076.
For a rough check by age, the page also shows Fidelity's milestones. They are savings equal to your salary by 30, three times your salary by 40, six times by 50, eight times by 60 and ten times by 67. They assume you save 15% of your pay from 25 and retire at 67.
What the calculator leaves out
The page calls itself an educational estimate, not financial advice. It leaves out taxes, investment fees, changes in your income and the timing of Social Security. Markets can also return less than either case.
The optimistic case is optimistic for good reasons. The S&P 500 fell 18.1% in 2022, and someone who invested at the start of 2000 had less at the end of 2009, even with dividends. Fees, taxes and selling in a downturn all pull a real investor below the index. The steady 4% case stands for a mix of stocks and bonds, which is steadier but usually grows more slowly.
Where the figures come from
The S&P 500 figures come from Robert Shiller's market data. From 1957 to 2026 the index returned about 10.7% a year with dividends reinvested, or about 6.8% a year after inflation. The 25-times goal follows the 4% rule from William Bengen's 1994 research. In it, a first-year withdrawal of 4% of savings, raised with inflation each year, lasted at least 30 years in US market history. The age milestones are Fidelity's.
All figures are in today's dollars. Returns are after inflation, and the calculator assumes your monthly saving rises with prices. Savings compound monthly, and each month's saving is added at the end of the month.
Use it on your own site
The retirement calculator is free to embed on a blog or site with copy-and-paste code, with no ads or tracking. See how to embed it.
Source: S&P 500 returns since 1957, from Robert Shiller's data, 1957 to 2026; Fidelity, How much do I need to retire?. Figures are educational estimates, not financial advice.