Investment calculator.

How investment growth works

An investment grows in two ways: the return on the money already invested, and the new money you add along the way. Both compound, meaning this year you earn a return on last year’s returns as well as on your original stake. The longer the money stays invested, the more of the final balance comes from growth rather than your contributions.

The schedule above makes that shift visible. In the early years your contributions are most of the balance; later, the growth column pulls ahead and keeps widening, because it is now earning on a much larger base.

What return rate should you use?

A return assumption drives the whole projection, so keep it realistic. The US stock market has returned roughly 10% a year on average before inflation over the long run, or about 7% after inflation. Bonds return less, cash less again. Many planners use 6% to 7% to stay on the cautious side.

Whatever you pick, remember it is an average, not a promise. Real returns swing from large gains to losing years, and past performance does not guarantee future results. Running a lower rate as well shows you a more conservative outcome.

The power of regular contributions

Adding a fixed amount on a regular schedule is called dollar-cost averaging. Because you buy at many different prices over time, you avoid the trap of putting everything in at a peak, and you remove the temptation to guess the perfect moment. Consistency tends to beat timing.

Small contributions add up more than people expect, because each one gets its own run of compounding. Increasing the amount a little whenever your income rises accelerates the balance without straining your budget.

Risk, return and diversification

Higher expected returns come with higher risk, usually felt as bigger swings in value. A portfolio of many investments, spread across companies, sectors and asset types, is diversified, which lowers the chance that any single holding sinks the whole plan. Diversification does not remove risk, but it tames it.

Your time horizon matters. Money you will not touch for decades can ride out the swings of higher-return assets; money you need soon is usually better kept safer, so a market dip does not force you to sell at the wrong time.

Fees, taxes and inflation

Three quiet forces reduce what you actually keep. Fund fees compound against you the same way returns compound for you, so a low-cost fund can be worth a large amount over decades. Taxes apply to gains unless the money sits in a tax-advantaged account like an IRA or 401(k). Inflation erodes what each dollar buys.

This calculator shows nominal growth at the rate you enter. To see real purchasing power, enter a return that already subtracts inflation and fees, which gives a more honest picture of what the balance will be worth.

Common ways to invest

The calculator works for any investment with a fairly steady return, but the real options sit on a ladder of risk and reward. At the safer end are savings accounts, CDs and money-market accounts, which pay modest, predictable rates and are often insured. A step up are bonds, which are loans to governments or companies that pay interest, with safer issuers paying less and riskier ones paying more.

Higher up are stocks, a share of ownership in a company, usually held through low-cost index funds or ETFs that spread your money across hundreds of companies at once. Real estate, owned directly or through REITs, and commodities such as gold round out the menu. Most long-term investors blend several of these to balance growth against risk.