Future Value ≈ Contribution × [(1 + r)^n − 1] ÷ r (for a stream of equal annual contributions at return rate r over n years)
The Short Version
Retirement planning is fundamentally a math problem about compounding — earning returns not just on your original contributions, but on all the previously earned returns too. Because of this, starting early matters enormously more than the exact amount contributed in any single year; a modest amount invested young can outgrow a much larger amount invested later, purely due to extra decades of compounding.
Explain It Like I'm 10
Imagine planting a tree. A tree planted today has decades to grow tall and wide, even if you only water it a little each week. A much bigger tree planted just a few years before you need shade will still be smaller than the one that's had 40 years to grow, no matter how much you water it in that short window. Retirement savings work the same way — the biggest factor isn't how much you 'water' it each year, it's how many years it's had to grow at all.
Step-by-Step Example
- 1 Person A invests $5,000/year starting at age 25, earning an average 7% annual return, for 40 years until age 65.
- 2 Their ending balance is roughly $1,000,000, the vast majority of which came from investment growth, not the contributions themselves.
- 3 Person B waits until age 45 to start, investing the same $5,000/year at the same 7% return, for 20 years until age 65.
- 4 Their ending balance is roughly $205,000 — despite contributing the exact same amount per year, half the time produced less than a quarter of the result.
- 5 To catch up to Person A's outcome, Person B would need to save far more than double per year — illustrating why starting early outweighs almost any other single retirement-planning decision.
$5,000/year invested at 7% for 40 years grows to roughly $1,000,000; the same $5,000/year for only 20 years grows to roughly $205,000 — half the time produces far less than half the result.
Quick Recap
- ✓ Time in the market typically matters more than the exact return rate or contribution amount — starting 10 years earlier can matter more than doubling your contribution later.
- ✓ A common rough retirement savings guideline is to aim for annual contributions in the range of 10–15% of income, adjusted for individual circumstances.
- ✓ 'Sequence of returns risk' matters more near and during retirement — a market downturn early in retirement, while withdrawing funds, can be far more damaging than the same downturn earlier while still contributing.
- ✓ Retirement planning isn't only about the accumulation phase — it also requires planning a sustainable withdrawal rate so savings last through retirement.