Four complete growth scenarios
These are the same scenarios used in the printable compound interest table. Each row shows the opening balance so the result can be reproduced.
| Starting balance | Monthly deposit | Nominal annual rate | Years | Final balance |
|---|---|---|---|---|
| $1,000 | $100 | 4% | 10 | $16,215.81 |
| $1,000 | $250 | 5% | 10 | $40,467.58 |
| $5,000 | $250 | 6% | 10 | $50,066.82 |
| $10,000 | $500 | 6% | 10 | $100,133.64 |
Compare the final balances
The bars compare whole scenarios. More than one input changes between most rows, so they do not isolate the effect of interest rate alone.
Assumptions behind every row
Each example uses a constant nominal annual rate divided by 12. Interest is added first, then the monthly deposit is added at the end of the month. Ten years means 120 deposits. Starting balances are shown explicitly; no tax, fees, inflation, withdrawals or changing returns are included.
Next balance = current balance × (1 + annual rate ÷ 1,200) + monthly deposit. The annual rate is entered as a percentage, so 4 means 4%. Calculations retain full precision and only the displayed result is rounded to cents.
| Scenario | Cash contributed | Estimated growth |
|---|---|---|
| Starter | $13,000 | $3,215.81 |
| Builder | $31,000 | $9,467.58 |
| Larger opening balance | $35,000 | $15,066.82 |
| Doubled plan | $70,000 | $30,133.64 |
Worked check: $1,000 plus $100 a month
At 4% a year, month one is $1,000 × (1 + 4 ÷ 1,200) + $100 = $1,103.33, rounded. Repeating the same unrounded calculation for 120 months gives $16,215.81. Cash contributed is $1,000 + 120 × $100 = $13,000, so estimated growth is $3,215.81.
Related tools and guides
Frequently asked questions
Is the annual rate an effective annual return?
No. These examples divide a nominal annual percentage by 12. An effective annual return needs conversion before it can be compared on the same basis.
Why are the last two balances exactly doubled?
Their rate and time are identical, and both the opening balance and monthly deposit are doubled. This model is linear in those two amounts, so the projected balance doubles too.
Will a real account achieve these balances?
The arithmetic follows the stated assumptions. Real rates, investment returns, contribution dates, charges and taxes can differ; these are illustrations, not forecasts.
Sources and method
- Compound Interest Calculator methodology - These tables use the same monthly recurrence as the calculator. Values were also checked with the future-value annuity formula.