Finance
Calculate your investment growth with regular contributions and compound interest.
End Balance
$299,160$
Your investment value after 20 years with monthly contributions
This calculator uses compound interest formulas. Actual returns may vary based on market conditions, fees, and reinvestment practices. Past performance does not guarantee future results.
An investment calculator is a financial tool that projects the future value of your investments based on your starting capital, regular contributions, and expected annual returns. It applies the compound interest formula to show how money grows exponentially over time—the longer you invest, the more interest compounds on your interest. Unlike simple interest, which only grows your initial amount, compound interest accelerates growth dramatically, making it essential for long-term wealth planning.
Enter your starting investment amount, the size of regular contributions (monthly or annually), your expected annual return percentage, and investment time period in years. The calculator computes two components: the future value of your initial lump sum and the future value of your recurring contributions, combined with compound interest. It then displays your projected end balance, total contributions invested, and interest earned.
FV = P(1 + r)^t + PMT × [((1 + r/n)^(n×t) - 1) / (r/n)]FV is your final balance, P is your starting principal, r is the annual return rate (as a decimal), t is years, n is contribution frequency per year (12 for monthly, 1 for annual), and PMT is your contribution amount. The first term calculates lump-sum growth; the second calculates the future value of your annuity (regular contributions).
| Input | Result | Notes |
|---|---|---|
| Starting £10,000, £500 monthly, 7% annual return, 20 years | £318,545 | Starting with £10k and adding £500 monthly grows to over £318k in two decades, with £178,545 earned as interest. |
| Starting $25,000, $1,000 annually, 6% annual return, 10 years | $39,687 | Annual contributions with steady returns show slower growth but still compound effectively, earning $3,687 in interest. |
| Starting €5,000, €200 monthly, 5% annual return, 30 years | €150,245 | Over three decades, consistent monthly contributions and compound interest transform €5k into €150k, despite a modest 5% return. |
Historical averages vary: diversified stock portfolios average ~10%, bonds ~5–6%, balanced funds ~7%. Conservative estimates of 5–7% are safer than aggressive assumptions; always consult a financial adviser for personalised guidance.
Monthly contributions are usually better because you invest smaller amounts regularly (dollar-cost averaging), which smooths out market volatility. Annual contributions work if a large annual sum is easier for your cashflow.
This calculator assumes fixed, consistent returns and contributions. Real-world returns fluctuate monthly; this shows an average. It's excellent for planning but not a guarantee—market conditions, fees, and taxes will affect actual results.
No—this calculator shows gross returns. Actual net returns will be lower after investment fees, advisory costs, and taxes. Check your specific investments for their expense ratios.
This calculator assumes consistent contributions throughout. If you plan to stop early, run two calculations: one for years 1–5 (then use that end balance as the starting amount for a second calculation with 0 contributions for years 6+).
Compound interest means you earn returns not just on your initial investment, but also on your accumulated interest. This creates exponential growth—the longer you wait, the more powerful the effect. That's why starting early matters so much.