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Compound interest calculator

Model how contributions and investment growth can compound over time with a clear split between money added and growth earned.

Create a free account to save your results, track progress over time, and unlock guide-connected features.

Compounding frequency

Scenario assumptions

$57,254
Final portfolio value
$10,000
Total contributed
$47,254
Total growth
82.5%
Growth share
$47,254
Growth from initial amount
$0
Growth from contributions

Contributions vs growth

YearContributedGrowthBalance
1$10,000$723$10,723
2$10,000$1,498$11,498
3$10,000$2,329$12,329
4$10,000$3,221$13,221
5$10,000$4,176$14,176
6$10,000$5,201$15,201
7$10,000$6,300$16,300
8$10,000$7,478$17,478
9$10,000$8,742$18,742
10$10,000$10,097$20,097
11$10,000$11,549$21,549
12$10,000$13,107$23,107
13$10,000$14,778$24,778
14$10,000$16,569$26,569
15$10,000$18,489$28,489
16$10,000$20,549$30,549
17$10,000$22,757$32,757
18$10,000$25,125$35,125
19$10,000$27,665$37,665
20$10,000$30,387$40,387
21$10,000$33,307$43,307
22$10,000$36,438$46,438
23$10,000$39,795$49,795
24$10,000$43,394$53,394
25$10,000$47,254$57,254

Scenario comparison

Decision scenarios

Stress case

$17,526

4% return with a 25% drawdown in year 5.

Base case

$49,320

Return net of 0.2% fees and 0.4% tax drag, with contributions rising 3%/yr.

Upside case

$103,900

10% gross return under stronger market conditions.

Risk flags

No monthly contribution is set, so the plan depends entirely on the starting balance and market returns.

Action plan

  1. 1. Add roughly $3,169/month before growth effects to close the base-case target gap.
  2. 2. Keep all-in drag below 0.6%/yr or model a lower expected return.
  3. 3. Review whether a 25% drawdown in year 5 would change the timeline or contribution plan.

Goal-based mode

$1,842
Required monthly contribution
Current savings progress1.0%

Adding $250/month reaches the goal about 1.3 years earlier.

Lump sum vs DCA

Lump sum
Winner
$96,930
Lump sum final
$93,897
DCA final
$3,033
Difference

Lump sum often wins because more money spends more time invested, though DCA can reduce regret and timing risk.

Fee impact calculator

$81,165
Value without fee
$4,700
Fee cost
$79,964
0.05% index
$64,892
0.75% active
$51,874
1.5% active

How to use the compound interest calculator

Enter your starting amount, monthly contribution, assumed annual return, time period, and compounding frequency. The chart separates your own contributions from investment growth so the source of the final portfolio value is easy to inspect.

Monthly compounding applies growth each month after the monthly contribution. Annual compounding applies the annual return at the end of each year. Real investment accounts can behave differently because market returns vary, fees reduce returns, and deposits may happen on different days.

Use this as a scenario model. Try conservative, moderate, and ambitious return assumptions to understand which part of the outcome depends on your savings behaviour and which part depends on market performance.