Compound growth calculator
How a starting balance and steady yearly saving grow at a fixed return, and how much of the result is growth on growth.
Your numbers
0% adds the same amount every year.
For the today’s-dollars figure.
Result
After 30 years
$662,724
$315,949 in today’s dollars.
- You put in
- $190,000
- Growth
- $472,724
- Share from growth
- 71%
- Doubles every
- 10.2 years
| Year | Contributions | Growth | Total |
|---|---|---|---|
| 0 | $10,000 | $0 | $10,000 |
| 3 | $28,000 | $4,215 | $32,215 |
| 6 | $46,000 | $13,429 | $59,429 |
| 9 | $64,000 | $28,768 | $92,768 |
| 12 | $82,000 | $51,609 | $133,609 |
| 15 | $100,000 | $83,642 | $183,642 |
| 18 | $118,000 | $126,933 | $244,933 |
| 21 | $136,000 | $184,018 | $320,018 |
| 24 | $154,000 | $258,001 | $412,001 |
| 27 | $172,000 | $352,683 | $524,683 |
| 30 | $190,000 | $472,724 | $662,724 |
RetirementPace is an educational tool, not financial, tax or legal advice. RetirementPace is not a registered investment adviser.
Track whether you stay on pace
A calculator answers today. Pace is whether you’re still on track next month and next year. Save this as a plan in the free planner (it stays in your browser), and soon record your real balances each month to see if you’re ahead or behind.
How it works
Each year the balance at the start earns the full year’s return, and that year’s contribution, added through the year, earns half of it: end = start × (1 + r) + added × (1 + r/2). The contribution then rises by the increase you enter. Today’s dollars divide each year’s balance by the inflation since now. The doubling time is ln 2 ÷ ln(1 + r).
Worked example
$10,000 to start and $6,000 a year at 7% for 30 years grows to $662,724, or $315,949 in today’s dollars at 2.5% inflation. $190,000 of that is money put in and $472,724 is growth.
Questions
What is compound growth?
Growth on growth. Each year’s return is earned not only on what you put in but on the returns already earned, so the balance grows faster the longer it is left. Over long periods most of a balance can be growth rather than contributions.
What is the rule of 72?
A quick way to estimate how long money takes to double: divide 72 by the yearly return in percent. At 6% that is about 12 years; at 8%, about 9. The calculator shows the exact figure for the rate you enter.
Why show today’s dollars?
Because prices rise. A balance in 30 years’ time will be a bigger number than it would buy today. Dividing by the inflation you enter shows what it would be worth in today’s money, which is the figure to compare with what things cost now.
Is a 7% return realistic?
It is an assumption, not a forecast. Long-run stock returns have averaged more than that in the US, bonds less, and fees and a mix of the two bring a portfolio’s figure down. Real returns also arrive unevenly; the retirement calculator shows what that does to a plan.
When are contributions added?
Through the year, so each year’s contribution earns half a year of growth in the year it goes in and a full year after that. This is the same convention the planner uses, and sits between adding everything on 1 January and everything on 31 December.