Five more years of work
20 years gives 20.0 years. 25 years gives 25.9 years — a difference of 5.9 years more (+29.6%).
Five more years adds contributions, compounds the pot longer and removes five years of drawdown — which is why it moves the answer more than any other input.
| Input | 20 years | 25 years |
|---|---|---|
| Saved so far(usd) | 150,000 | 150,000 |
| You add each month(usd) | 800 | 800 |
| Years until you retire(years) | 20 | 25 |
| Return before retirement(percent) | 6.5 | 6.5 |
| Return after retirement(percent) | 4.5 | 4.5 |
| Monthly spending, in today’s money(usd) | 4,500 | 4,500 |
| Social Security and pensions, today’s money(usd) | 2,000 | 2,000 |
| Inflation(percent) | 3 | 3 |
| Years the savings last | 20.0 years | 25.9 years |
Every figure, both ways
| Step | 20 years | 25 years | Difference |
|---|---|---|---|
| What today’s savings grow to | 548,467.01 | 758,429.68 | +209,962.67 |
| What future contributions grow to | 392,336.74 | 599,069.22 | +206,732.48 |
| Savings at retirement | 940,803.75 | 1,357,498.9 | +416,695.15 |
| The same spending, in retirement-year dollars | 8,127.5 | 9,422 | +1,294.5 |
| Social Security and pensions, in the same dollars | 3,612.22 | 4,187.56 | +575.33 |
| What the savings have to cover each month | 4,515.28 | 5,234.44 | +719.17 |
| Years the savings last(years) | 20.01 | 25.93 | +5.92 |
| What the 4% rule would allow a month | 3,136.01 | 4,525 | +1,388.98 |
| Monthly gap against that rule | 1,379.27 | 709.45 | -669.82 |
Questions people actually ask
- Does raising years until you retire change the answer in proportion?
- No, and that is the point of putting them side by side. Years until you retire changes by 25% while years the savings last changes by 30%. The step table below shows which line breaks the proportion.
- What is held constant between the two columns?
- Everything except years until you retire: saved so far, you add each month, return before retirement, return after retirement, monthly spending, in today’s money, social security and pensions, today’s money, inflation. That is what makes the difference attributable — change two things at once and neither column tells you which one moved the answer.
- Can I compare my own two numbers?
- Yes, from the address bar: add ?a.years_to_retirement=… and &b.years_to_retirement=… to set each side, and a parameter without a prefix sets both at once. The page is computed per request, so any pair works — these two are only the ones worth a link.
Change either side by adding query parameters — ?a.years_to_retirement=… and b.years_to_retirement=…. A parameter without a prefix sets both sides at once. Source: US SEC Investor.gov — retirement planning, Social Security Administration — benefit calculators, US Bureau of Labor Statistics — Consumer Price Index