Compound interest calculator
How much could my money grow?
Enter a starting balance, a regular contribution and an assumed return to see the balance year by year — and the year cumulative growth finally overtakes cumulative contributions.
- Written by
- Suggested Investments Research Team
- Content type
- Calculator
- Published
- 2026-09-13
- Last reviewed
- 2026-09-13
Your assumptions
A commonly used illustration rate. These are inputs to a hypothetical calculation, not expected or guaranteed returns.
Projected portfolio
$691,150
After 30 years, monthly contributions.
Money you contributed
$190,000
Estimated investment growth
$501,150
From contributions
27.5%
From growth
72.5%
Investment multiple
3.64×
The compounding crossover
Year 17
The point where hypothetical growth becomes larger than the money you personally added.
Compound growth
Portfolio value against the money you contributed. The vertical marker is the compounding crossover.
Hypothetical illustration based on the assumptions entered above. It is not a projection of actual results, and it does not include taxes or trading costs. Past performance does not guarantee future results.
Contributions and growth, separated
Wealth comes from both saving and returns. The lower band is your own money.
What can waiting cost?
The same plan, the same assumptions, measured at year 30. Only the start date changes.
Start today
$691,150
Reference
Start in 1 year
$638,777
$-52,374 vs starting today
Start in 5 years
$462,290
$-228,860 vs starting today
Start in 10 years
$300,851
$-390,300 vs starting today
Time itself is a major component of compounding. These are hypothetical mathematical projections, not predictions, and they assume contributions only begin at the chosen start date.
How to read the result
- Compare the contributions line with the growth line. Early on, contributions dominate; the crossover is where compounding becomes the larger force.
- Change the fee input before you change the return input. Fees are the assumption you actually control.
- Look at the last five years of the projection: that is where most of the final balance is created, which is why exiting early is so expensive.
What this calculator cannot tell you
- Returns are assumed to be smooth. Real markets deliver the same average through wildly uneven years, including losses.
- Taxes are not modelled, and account type changes the outcome materially.
- This is arithmetic on your inputs, not a projection of any specific investment.
Terms used here
Sources and methodology
Standard future-value arithmetic. Every figure is hypothetical and depends entirely on the assumptions you enter.
- Investor.gov investor education — U.S. Securities and Exchange CommissionPrimary source
- Intelligent Accumulation methodology — Suggested InvestmentsPrimary source
Keep reading
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