Ten more years of payments
20 years gives $3,163.25. 30 years gives $2,533.43 — a difference of $629.82 less (-19.9%).
The same pot stretched over half again as long — the payment falls, but the total paid rises, because the unspent balance keeps earning.
| Input | 20 years | 30 years |
|---|---|---|
| Lump sum(usd) | 500,000 | 500,000 |
| Annual return while it pays out(percent) | 4.5 | 4.5 |
| Years of payments(years) | 20 | 30 |
| Monthly payment | $3,163.25 | $2,533.43 |
Balance left, side by side
Every figure, both ways
| Step | 20 years | 30 years | Difference |
|---|---|---|---|
| Monthly payment | 3,163.25 | 2,533.43 | -629.82 |
| A year of it | 37,958.96 | 30,401.12 | -7,557.84 |
| Paid out over the whole term | 759,179.25 | 912,033.56 | +152,854.31 |
| Of that, interest | 259,179.25 | 412,033.56 | +152,854.31 |
| Monthly income if you never touch the capital | 1,875 | 1,875 | 0 |
Questions people actually ask
- Does raising years of payments change the answer in proportion?
- No, and that is the point of putting them side by side. Years of payments changes by 50% while monthly payment changes by 20% in the opposite direction. The step table below shows which line breaks the proportion.
- What is held constant between the two columns?
- Everything except years of payments: lump sum, annual return while it pays out. 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=… and &b.years=… 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=… and b.years=…. A parameter without a prefix sets both sides at once. Source: US SEC Investor.gov — annuities, FINRA — annuities