Which tab should I use?

The tab names the unknown you want solved. Know your starting amount, contributions, rate and time, and want the outcome? End Amount. Have a target and want the monthly contribution, the return, the starting sum, or the time it takes? Pick the tab with that name and the calculator solves for it, holding the others as you entered them.

What return rate is realistic?

For planning, not prediction: U.S. stocks (the S&P 500) have returned roughly 10% a year nominal over long spans, with deep drawdowns along the way; high-quality bonds and CDs typically sit several points lower with far less drama. A balanced portfolio is often modeled at 5–7%. If a plan only works at 12%+, the plan — not the calculator — is the problem.

Does this calculator include taxes and inflation?

No — it works in nominal, pre-tax terms, like most return planning. If taxes on interest and inflation matter to your question, the Interest Calculator runs the same compounding engine with a tax rate skimmed as interest accrues and an inflation-adjusted buying-power result.

Why does it say my target can't be reached?

Because with the other inputs fixed, the math never gets there — for example, a target below what your starting amount and contributions already guarantee would need a negative return, or a target so high that even 100 years of growth at the entered rate falls short. Loosen one input (more time, more contributions, or a smaller target) and solve again.

Investment Calculator

One investment, five possible unknowns. Pick the tab named after the thing you want to find — the calculator solves for it and holds everything else as entered.

Your Target

Starting Amount

After

years

Return Rate

Compound

Additional Contribution

Contribute at the

beginning end

of each

month year

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Investing Is Four Numbers and a Decision

Strip any investment down and five quantities describe it: a starting amount (the principal — savings, an inheritance, the price of an asset), a return rate (the percentage that does the compounding, and the figure everyone compares investments by), an end amount (the target or the outcome), an investment length (more periods means more compounding — and more exposure to an unforeseeable future), and additional contributions (the annuity payments, in finance jargon, that most real plans are actually built on). Fix any four and the fifth is determined — which is exactly what the five tabs above do. The calculator is the easy part; the sections below are about choosing honest values for the variables.

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CDs and savings vehicles: the low-risk shelf

A certificate of deposit is the textbook fixed-rate investment: a fixed return for a fixed length, insured in the U.S. by the FDIC up to $250,000 per depositor per bank, with longer terms generally paying higher rates. Savings and money market accounts are its liquid cousins — lower rates, no lockup. These fit the calculator perfectly because both the rate and the length are known in advance; there is no guessing, only arithmetic.

Bonds: lending, graded

A bond is a loan you make to a company or government, and its return is compensation for the risk they might not pay you back. Rating agencies (Moody's, S&P, Fitch) grade that risk: highly rated issuers borrow cheaply and safely; low-rated ("high-yield") issuers pay handsomely for the danger. Prices move opposite to interest rates, which matters if you sell early; held to maturity, a bond simply pays its coupons — usually twice a year — and returns face value. One special case deserves note: TIPS, U.S. Treasury inflation-protected securities, whose principal adjusts with the Consumer Price Index — a government-guaranteed return that keeps pace with inflation by construction, at the price of a modest base rate.

Stocks and funds: owning, not lending

A stock is literally a percentage of a company: shareholders share profits through dividends and through whatever a future buyer will pay for the share. Returns are not fixed — which is why the Return Rate tab exists: to ask what rate a goal requires, before asking whether the market is likely to grant it. Most investors hold stocks through funds: mutual funds pool many stocks under a manager for a fee (sometimes a sales "load"), while ETFs trade like a single stock and track an index, sector, or asset class — the S&P 500 being the canonical benchmark, with its roughly 10% long-run nominal average and its very real crashes inside that average.

Real estate and commodities

Property invests two ways: appreciation (flipping, or holding while an area develops) and income (rent) — often both, with leverage amplifying each; our rental property calculator models that properly, and the real estate hub collects the housing tools. REITs package the same exposure for people who prefer not to unclog anything. Commodities are the wilder shelf: gold, whose value rests on scarcity and fear — it reliably spikes in wars and crises; silver, half precious metal and half industrial input (solar panels, cars); oil and gas, usually traded on spot and futures markets rather than held, with prices set by the global economy's mood. All of them can be fed into this calculator as a starting amount and an assumed return — and all of them punish a careless assumption.

The honest caveat

There is no "right" set of inputs. Use a historical average return for a house, a forecast for a business, include every capital expenditure or only one cash-flow stream as "contributions" — each choice is defensible and each changes the answer. Treat results as scenarios, not prophecies: solve for the return your goal needs, then judge whether that return is plausible; solve for the contribution, then judge whether your budget survives it. And before using this general tool on a specific job, check the financial calculators list — a purpose-built calculator (mortgage, rental property, retirement) will usually model the details this one deliberately leaves out.

FAQ

Which tab do I want?

The one named after your unknown. Everything else you enter is treated as given.

What return should I assume?

Long-run ballparks: ~10% nominal for U.S. stocks, several points less for bonds and CDs. If your plan needs 12%+ to work, fix the plan, not the input.

Taxes and inflation?

Not here — this is the nominal planner. The interest calculator runs the same engine with tax skimmed as it accrues and a buying-power result after inflation.

It says my target can't be reached?

With the other inputs frozen, the math never arrives — the target is below what's already guaranteed, or beyond 100 years of growth. Loosen an input and solve again.

Disclaimer: This calculator provides estimates for educational purposes only and does not constitute financial advice. It assumes a fixed rate of return; real investments vary year to year, and past performance does not predict future results.