Compound Interest Calculator — Future Value and Long-Term Growth

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Compound growth over time

Results summary

30 Years

End balance
$154,886.21
Starting amount
$10,000
Total contributions
$36,000
Total growth
$108,886.21
Yearly compound breakdown
YearContributionsGrowthBalance
1$11,200$632.65$11,832.65
2$1,200$742.61$13,775.26
3$1,200$859.17$15,834.43
4$1,200$982.72$18,017.15
5$1,200$1,113.68$20,330.83
6$1,200$1,252.51$22,783.34
7$1,200$1,399.65$25,382.99
8$1,200$1,555.63$28,138.62
9$1,200$1,720.97$31,059.59
10$1,200$1,896.23$34,155.82
11$1,200$2,082$37,437.82
12$1,200$2,278.93$40,916.75
13$1,200$2,487.65$44,604.40
14$1,200$2,708.92$48,513.32
15$1,200$2,943.45$52,656.77
16$1,200$3,192.06$57,048.83
17$1,200$3,455.58$61,704.41
18$1,200$3,734.92$66,639.33
19$1,200$4,031.01$71,870.34
20$1,200$4,344.88$77,415.22
21$1,200$4,677.56$83,292.78
22$1,200$5,030.22$89,523
23$1,200$5,404.04$96,127.04
24$1,200$5,800.27$103,127.31
25$1,200$6,220.29$110,547.60
26$1,200$6,665.51$118,413.11
27$1,200$7,137.44$126,750.55
28$1,200$7,637.69$135,588.24
29$1,200$8,167.95$144,956.19
30$1,200$8,730.02$154,886.21

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About this compound interest calculator

Compound interest means earning growth on top of earlier growth. Your balance generates returns, and future returns are calculated on a steadily increasing base. This calculator projects investment growth using monthly compounding, with optional recurring contributions.

How the math works

We convert the annual return into an effective monthly rate and apply monthly compounding. Contribution frequencies are normalized to a monthly pace so results stay comparable. Outputs are summarized per calendar year in a stacked chart showing Starting amount, Contributions and Growth.

Tips

What is compound interest?

With compounding, returns are earned on both your original principal and on previously earned returns. Over longer time horizons, this effect becomes the main driver of growth.

The math (lightweight)

We convert your annual return r to an effective monthly rate m using m = (1 + r)^(1/12) − 1, then apply monthly compounding. Over Y years, this results in 12 × Y compounding steps.

Quick example

Start with $10,000 at a 6% annual return for 30 years with no additional deposits. The balance grows to roughly $57,000. Adding $200 per month can push the end balance toward the $250,000 range, thanks to compounding on both principal and contributions.

Compounding frequency

More frequent compounding, such as monthly instead of yearly, slightly increases the effective return. We standardize on monthly compounding to keep the yearly schedule clear and consistent.

Using this calculator

  • Enter a Starting amount (this can be $0).
  • Choose the number of Years and an Annual return (%).
  • Add an optional Recurring contribution and select its frequency.
  • Click Calculate to view the chart and yearly breakdown.

Inputs explained

  • Annual return (%): a planning average, converted to a monthly rate for compounding.
  • Contribution frequency: weekly, biweekly, semimonthly, monthly, quarterly or annual contributions are normalized to monthly.
  • Currency: display only. No exchange-rate projections are applied.

Practical tips

  • Time matters most: starting earlier often outweighs starting with a higher amount.
  • Stress-test assumptions: try several return scenarios, such as 4%, 6% and 8%.
  • Keep costs low: fees and taxes reduce effective returns over time.

Assumptions & limitations

  • No taxes or trading frictions are modeled. Lower the return input to approximate net results.
  • Results are nominal and do not account for inflation.
  • Past performance does not guarantee future results. Use outputs as planning illustrations.

Want to run other scenarios?

Glossary & Q&A