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Investing Calculators

Free investing calculators to project growth, compare contributions, and understand compound interest.

Everything in this category runs on the same idea: money left to grow earns returns on its own returns, and the effect accelerates the longer it is left alone. What differs is the certainty. A savings account or a certificate of deposit pays a rate the institution contractually commits to, so the projection is close to a forecast. An investment return is an assumption about uncertain markets, so the same arithmetic produces a scenario rather than a promise. These calculators keep that distinction visible instead of blurring it.

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CentCompass
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Calculators

When to use each calculator

Compound Interest Calculator
Use it to understand the mechanism itself — how contributions, rate, and time interact, and why the final years of any projection contribute so much more than the first.
Savings Calculator
Use it for money in a deposit account with a published APY, such as an emergency fund or a house deposit you are building.
CD Calculator
Use it when you can lock a lump sum for a fixed term. It shows the value at maturity and the total yield, which is usually higher than a savings account pays.
Investment Calculator
Use it for a long-horizon portfolio where you supply an assumed return. It separates what you contributed from what growth produced.

Choosing between them

Savings or CD?

A CD generally pays more but locks the money for a fixed term, with a penalty for withdrawing early. A savings account pays less and stays liquid. Money you might need soon belongs in savings; money you can genuinely commit earns more in a CD.

Compound interest or investment calculator?

The mathematics is identical — the difference is what the rate means. Use the compound interest calculator when the rate is contractual, and the investment calculator when you are modelling an expected market return that may not arrive on schedule.

Should this money be invested at all?

Horizon decides it. Cash needed within a few years belongs somewhere safe and liquid, because a downturn at the wrong moment is unrecoverable. Money with a decade or more ahead of it has time to absorb volatility, which is where an invested account historically outperforms deposits.

Guides

  • Compound Interest ExplainedWhy growth on prior growth eventually dwarfs your own contributions, how the formula works variable by variable, and what APY really means.
  • Dollar Cost Averaging ExplainedInvesting a fixed amount on a fixed schedule, what the evidence says about it versus investing a lump sum, and when each approach makes sense.

Explore more

Browse every calculator on the site, read our financial guides, or see how CentCompass is built and reviewed.

Frequently asked questions

What return should I assume?

For deposit accounts, use the APY the institution publishes. For investments, many long-term plans model something in the range of 6–8% nominal for a diversified stock portfolio, based on multi-decade averages — actual returns vary enormously year to year.

Do these results account for inflation?

No. Every projection here is in nominal dollars. To think in today's purchasing power, subtract an assumed inflation rate from your return and model with that lower real rate instead.

Are the returns taxed?

In a taxable account, interest is generally taxed in the year it is credited and investment gains when realised. Tax-advantaged accounts such as a 401(k) or IRA defer or eliminate that drag, which is a large part of their long-run advantage.

Why does the balance grow so slowly at first?

Because a percentage return on a small balance is a small number of dollars. As the balance builds, the same percentage produces far more, which is why most of the growth in any long projection appears in the final years.

Is my deposit protected?

Deposits at FDIC-insured banks and NCUA-insured credit unions are protected up to the applicable limits per depositor and ownership category. Investment accounts carry no such protection against market losses.

Sources

How this page is produced

Editorial process. CentCompass is maintained independently, and this page is written and checked against the official publications listed above before it goes live. There is no separate editorial reviewer. This page was last checked on . See our editorial policy.

How the calculations work. Every result comes from a small, unit-tested calculation engine rather than a spreadsheet or a hardcoded table. Loans use the standard amortization formula, growth uses compound-interest math, income tax applies the federal progressive brackets, and payroll applies Social Security and Medicare rules. Our methodology sets out each one.

Where the figures come from. Tax brackets, standard deductions, FICA parameters, and contribution limits are stored once in a dated registry and read directly by the calculators — the same values appear in the text above, so the two can never drift apart. Each figure records its source, effective tax year, and review status on our data sources page.

Update policy. Regulatory figures are checked against their primary source when the IRS, SSA, or another authority publishes new values — typically each autumn for the following tax year — and again at the scheduled review date recorded for each dataset. Figures that have not been checked yet are marked as draft on the data sources page until that check is complete.

Educational purposes only — not financial, tax, or investment advice (disclaimer).